I have Sirius sat radio. Today in a parking garage it was still working. How is !

I have Sirius sat radio. Today in a parking garage it was still working. How is that possible?

I had it happen before in a parking garage here in town and thought it must be a fluke. But both times there was obviously no path to the satellite. Heck I drive under a bridge on the highway and it cuts out so am stumped. I do not have one that records. Am in Austin Texas if that makes a difference.

You were probably getting a signal from a ground repeater, not from the satellites.