Has anyone experienced beneficial coin glitches?

I had 36 coins this morning. This afternoon, I put one Pokémon in a weak friendly gym near my house, went home, and watched it get attacked shortly after. I was busy so I couldn't run out to try to keep it afloat with berries. I then got a notification that my Pokémon had returned and I saw the gym switch teams.

My Pokémon was in there for 1 hour and 6 minutes. I am certain I did not have any other Pokémon in gyms. I kept refreshing to see if I received my measly one coin, but it remained stuck at 36. I closed the app and didn't open it again for several hours. When I opened it again later this evening, I was at 42 coins.

Not that I'm complaining, but what happened? Did they change the coin system or did the game just glitch and give me bonus coins? Has anyone else had this happen so far?