So this has happened to me more times than I can count and its seemingly random. I gather a node and use my GP, either entirely or partially, I switch jobs and enter a dungeon, raid, trial, etc. come out of that content about 10-15 minutes later and I still have that GP missing? I've even had it where I logged off, in a town for the night, log back in 8+ hours later, and my GP still hasn't come back.