I don’t know anything about the baseball bat in the back of the head pain.
However, I do know I also did something to my neck a couple times when I was starting out. Nothing as severe as described, but kind of a snap or crunch while straining to do a (heavy at the time) military press.
Since there wasn’t true pain and the exertion levels weren’t impeded it didn’t seem like anything serious. I had thought maybe several mostly unused muscles were fused and had seperated under the general strain.
The only problem I have these days is a nagging shoulder twinge. My theory is that years of reaching forward to use a mouse has my right shoulder out of alignment a bit, but that of course is a story for another thread…