Invoking bug?

praxismirrors

I logged on earlier today to play a bit before I left for work and I had two celestial coins. Before I logged of to go to work, a message popped up saying that my coins would expire in 15 hours. When I logged on after work about 5 hours later all my coins were gone... I'm curious as to why this happened when I should have had another 10 hours to invoke before my coins disapeared