Don't beat yourself up too bad, this could have happened to any of us at some point or other.
I recall making a fuel stop at Gatlinburg Tennessee's FBO one time on a cross country over the Smoky Mountains late in the afternoon. Sure enough the darn thing closed 5 minutes before I got there and I intended to keep going after fueling up. Luckily I was able to get fuel at a Knoxville FBO not far away without reaching fuel mins but it was looking like motel and cheese crackers there for a minute since they closed 10 minutes after I got fuel.
Airnav has customer reports attached to all the FBO's it lists, and most of them are accurate enough to be of value. Occasionally an FBO will claim to have services or times that it does not actually have, even to the point of blatant lying sometimes, so be aware of the value of the customer comments.