"The time I got a free 0.01 BTC"

— Can someone explain the following? —

One time I sent a Muun wallet lightning payment to another wallet I own. The 0.01 BTC payment arrived in the other wallet. But then Muun said the lightning payment failed and returned the 0.01 BTC back into the sending wallet. However, the 0.01 BTC was still in the receiving wallet. I had the original 0.01 BTC and had gained another 0.01 BTC. What to make of this?

#asknostr