Checking critical fasteners should be done more regularly than the maintenance schedule calls for. If you don't have a torque wrench handy, use fingers. If anything moves, there's a problem.
Glad you recovered before you really needed the brakes or the caliper got caught in the wheel. I was riding in a group last year and the guy in front of me had something hanging off of his swingarm. I thought he had picked up a clump of hay, or something. I got closer and realized that it was his rear brake caliper. I kept getting close to try and get his attention but I didn't want to get too close in case that sucker flew off and hit me. It was a tense couple of minutes, for sure.
P.S. IIRC, the left and right calipers are identical so just check the other side to see what should be where.
06 DL-650 - SilverBlue
05 DL-650 - red (RIP - watch your mirrors!)