So I bought the Fallout classic collection not so long ago. I have been playing the game for a while, and now I'm on the last two vault 13 missions/quests. I killed the Master (very very frustrating) and all that. Then I went to the Mariposa base with brotherhood paladins. They slaughtered the super mutants extremely quick. So I didn't think of it and left to help some of the towns. But that was a bad idea. I came back after a while and tried to open the door, and it said I needed a key. All the corpses were gone, so I looked around and nothing. Looked online and it said one of the guys had it, too bad he disappeared.

So how do I get into the base or get the holodisk to get the code???

The main mutant (nightkin looking guy with the Wattz Rifle), will have a disk that should allow entry. My guess is that the disk is hidden by his pool of blood. Check where the body was for the entry key. The same mutant also holds a radio that allows you to trick the mutants inside, making entry a bit less hectic in the beginning.

There is no pool of blood, and I couldn't use the radio as the Brotherhood Paladins just came in and started to kill everything. I might try to use a radio though and see what happens.

I encountered the same scenario and there is no way to get back in. I think maybe if you have high lockpick and some electronic lockpicks MK II's that may work.

Where could I get this electronic pick lock thing, I am not a high level, thus I have many probelms, so I can get my picklock pretty high.

You went to assault a super mutant stronghold, then decided to go and faff around in junktown or shady sands instead? lol

I dunno how to help you, since i guess the item you need has dissapeared, load a different save?

The electronic lock picks are a gift for successful completion of a quest

But if your skill is very very very high you may not need them.

Doing some quests for the theives guild will net you an electronic lockpick. From there you should be able to open up the door. You'll probably have to put some points in lockpick anyway (to at least get to 100).

Mariposa isn't something you want to do under level 18 or so. I usually save the Master for last... just talk him out of it.