I just got lucky enough to snag a fairy blade and was curious. :3

Nope, they're completely safe. Congratulations on the snag. :D

C: Thank you for telling me! I'm glad they are.

Items are only susceptible to RE's if they're unlocked in your Inventory; nothing can touch them anywhere else. Congrats! :)

If it is in your Inventory, lock it quickly, otherwise it is safe.