How can I find out if a Protection Order was filed against me by my ex-wife in Clark County Nevada?

Probably most-straight-forward wouild be to call the TPO office.  THe "Family Violence Interention Program" number is 702-455-3400; the "After Hours Protection Hotline" number is 702-646-4981.  There are more issues involved in TPOs relating to persons not within the jurisdiction of the court than can be adequately addressed by this email, and it is possible that it is something else -- you might want to call the Clerk of the Court -- 702-455-2591, and ask if any actions have been filed with you as a party.