so im dawnguard so i could get the xbow stuff and i had serana following me i havent finished any main story line quests yet and i was at gloombound mine and told her to wait outside while i mine the ebony and then i waited 72 hrs so the mine would replenish and i went out a dragon attacked and she was missing ive fast traveled a few times but i cant find her anywhere around gloombound does she return to the vampire castle or sumthing?

Don't know about serana, but just so you know mines take a full ingame month to replenish their ore.

i heard tat gloombound had a glitch where if u wait 72 hours, exit then reenter it would be replenished wasnt sure if it was true but i figured why not

she is originally found in http://www.rarityguide.com/articles/articles/2745/1/Skyrim-Dawnguard-Walkthrough-Part-3-Dimhollow-Cavern-Brazier-Puzzle-Solution/Page1.html so try there maybe she went back

If you are Dawnguard, she may be at the fort.....

Check the Dawnguard Fort, she's usually sitting on a bench in the hallway leading to the kitchen. It's dark so look around, she can be hard to spot if your not looking for her.

Good Luck