About 60 hours of playtime ago, I recieved the dragon priest mask from the main quest line 'nahkriin'. At the time I thought nothing of it and got rid of it. I cannot remember whether I dropped it or sold it, but now I realy want it back because I found out I need to get all 8 of them for the epic mask. Im kicking myself so hard right now, Ive checked the obvious places but no luck so far. Is there any way I can find it, or will it be gone by now?

I've gotten 4 already. I keep one in my inventory to use (it has +100% magicke regen) and put the rest in the treasure chest in my house.

I think youve pretty much lost it.
The monster that had it does not respawn.
If you sold it to a merchant, his inventory probably will have respawned by now.
If you dropped it somewhere, well, its a big place

If you sold it to a shopkeeper, chances are it's already vanished. If you're on the PC, you can give it to yourself through the console. Otherwise, nope. If you dropped it, though, it will be wherever you dropped it. Good luck finding it though!

If you're on PC you can just spawn one. On xbox, I guess the best you can hope for is that someone finds it and brings it to you.

spoiler?

Me too. I got 7 masks. Only to remember I placed the 8th mask on my dead necromancer thrall, which turned to ash at a point in the game that i was fortunately able to retrace my steps to; and unfortunatly find that the ashes have scattered to the wind. Super bummed. I really wish they'd have made special items respawn back to somewhere...

OH A SPOILER!!! NO!! THE DRAGON PRIESTS HAVE NOTHING TO DO WITH DRAGONS, DON'T WORRY SON!!

Don't worry about it. You can get them on the next playthrough. And here, to make you feel a little better about it, I brought you this! http://elderscrolls.wikia.com/wiki/Dragon_Priest_Mask_locations