Where did the mulch come from? It is not unusual to find a few bugs in a bag of mulch from Lowes, Home Depot, ect. They are harmless to your snake, although we still don't like them in there It is possible it was a mite...especially if the mulch came from a pet store. Mites can catch a ride on about anything!! You can bump into another snake owner in the grocery store...who has a snake with mites...mites on him, mite gets on you...mite gets on your snake. It's unusual to see just one, they multiply fast. Best place to look to comfirm your worries is the water bowl. If your snake is soaking you should find mites floating in the water if your snake has any. They drown.