Sure sounds like a pawl spring. Don't know of any other cause for this except the bolt that holds the shift lever in the trans is loose and it sounds like you checked that.
You did not cause this by not riding.
Since the repair is a disassembly of the trans most will opt to have the whole thing done anyway. Some riders will do the R&R and send the trans off for repair. If you think you could do this yourself at some later time there is no penalty for putting it off till you can do the work. How many miles on the trans?