Well, stuff happened like this:
My Khajit Dar'Jo and his mercenary Jenassa had some problems. Enemies overpowered them and they needed to sneak through the dungeon. But... Jenassa always grabs her mace when sneaking instead of her bow and thus alerted everyone. So, I gave her the only dagger I had at that moment: Mehrunes Razor.

After having raid 7-9 medium to large sized nordic ruins I decided to have my Razor back. Unfortunately, she didn't have it. I was pretty sure I never took it back from her, but still, I decided to check my containers at Dar'Jo's house. Nothing! I wanted to kill her. But because of Role-playing purposes I have decided to marry her and leave her to rot at Dar'Jo's house.

As soon as I get home IRL I will check every dungeon I raided. Every merchant I've been to. Do I have a chance of finding it? Does Mehrunes Razor dissappear from merchant inventories? I know journals don't dissappear.
And what if Jenassa was disarmed and never picked the Razor up, will it still be on the floor of the dungeon? Only a few days passed.

And no, I'm not able to spawn it because I play Dar'Jo on the PS3. To all other console users: Don't ever use followers! And if you use them for a pack mule or Role-playing, never give them Unique items and artifacts. I learned this the hard way.

On PC, you could teleport to the daggers actual location. Would have been interesting where you landed.

I doubt you will see your dagger again.

Nordic ruins you said? It's possible that your follower got disarmed by a draugr boss.

Yep ... in which case he will never find the dagger. Gosh, it's hard for me to find my sword sometimes after getting disarmed in those nordic ruins!

Yeah that is what most likely happened, a draugr shouted at your follower and she dropped it, not uncommon. If you're on pc, it's a simple matter of getting the item's ID from a wiki and putting it back in your inventory. If not on pc, well, you'd have to go crawl over every dungeon you been to inch by inch and hope it's still there.

I actually found it. It was laying around in Saarthal. Jenassa must've been disarmed. If you enter Saarthal at higher levels a Draugr Deathlord will spawn. So I got my Razor again! And Jenassa is home alone... Selling stuff... Cooking stuff... I might take her with me again after a while.

Wow, count yourself lucky! Those weapons are hard to find even when you know the room you are looking for it right after being disarmed. Talos is watching over you.

How long did it take you to find it?

Fortune did smile on you. I would actually go buy some lottery tickets!

I would def just smith some nice daggers for her or just purchase them =)

15 minutes. I just loaded previous save files to find out when she still had it and when she lost it. This way I reduced the amount of ruins I'd have to search through. Saarthal, and 2 other ruins were the candidates. Saarthal was the second one I checked. So yes, very lucky.

Most of the time the weapons are being Fus-Ro-Dah'ed to another plane of Oblivion. Luckily the draugr only used the disarm shout on her. I would've lost it otherwise.

I thought you were gonna say a few hours or something Lesson learnt not to give a follower an item of high value, eh? Good job finding it, though.

There's alot of good reasons why I don't take followers.

I normally kill the ones that aren't essentual and than take and sell their stuff. I feel that the followers who I take out in the wilderness and slit their throats; are dying in a way that contributes to my character. These followers are easy targets for black soul capping for the Black Star and black soul gems for character to use.

I really believe those are good reasons. I think my fellow members should be inclined to do the same as followers are only useful for such purposes. House carls are stupid and dull and the only useful purpose they have are either Boethia's quest to be sacrificed or be slapped in Azura's Black Star.

I feel I honor my followers as I kill them; because they are making Skyrim a better place.

I've never found Mehrunes Razor that useful. Admittedly, I haven't used it in Skyrim, but in Oblivion you could slash away for days and not get an insta-kill.

I haven't trusted followers since my Nord stopped on a cliff top to admire the view and Lydia stomped up and shoved him over the edge.

Never had much use for MR, but hey, i like to collect it though

I think MR is pretty nice weapon to look at, but I've found little use for it.

What would be nice if I could apply the 2% chance one hit kill enchantment to my swords from that little dagger. But my swords really don't need it because they have powerful enchantments on them already.