You may want to consider trying unplugging the tv's power cord for about ten minutes, which probably may reset the tv. I had a panny th50px77u years ago and the manual mentioned something about unplugging the tv. If you want, you can wait until I get home to recheck the manual to see what it says about unplugging the power cord. Let me know if you want me to look at my service manual.
Per manual: Exiting service tool or hotel mode in service menu = "Disconnect the AC cord from wall outlet" It doesn't specify how much time. You may be able to plug the tv's power cord right back into the wall outlet.