I recently started to decide to collect rare items found in caves/mines/temples/etc and i was wondering if you sold them to stores, would you have any chance of getting them back from another dungeon or store???

If you come back in less than 72 hours maybe after that I think the vendors inventory respawns. There are some items in Oblivion that are unique and there is only one copy. Most rare loot you could get another although that could take a long time.

Generic magical items yes, even the rare ones of them you can get copies of.

Example:

Ring of the Iron Fist.

Extremely rare and good magical ring. If you sell it, you can find another one. Likelihood of it happening? Not too likely at all. Even with the Blind Moth Prelate it would still take some time, however it is possible.


Now, something like Umbra? No. If you sell the strongest base damage one-handed weapon in the game, you will not get another copy. Nor will you get another copy of Spell Drinker or anything that comes from the daedric shrines. If you sell something truly unique then there is no getting it back.

Merchants sometimes do hold it in the inventory for a little while but I'm not sure how long.