I would talk to Bovada about it. Like EP, I've had random charges come up that were traced back to a waiter at a restaurant I ate at months before. It's often hard to track down the scammers but I think they'd still like to know either way. I know it's a bit stressful but your bank will sort it out for you. That's why we pay crazy interest and fees
ETA - I'd also look into the place you used it last, "the once in 4mths". In my case, that's exactly what happened to me. Scammers waited for awhile to try to jam me... I guess to try to make it look less obvious?