No T-Mobile WiFi Hotspot Anymore in Some Starbucks?

Yes, I know that:

– Starbucks changed WiFi hotspot providers last year and that AT&T provides the service now while T-Mobile Hotspot users have about 4 years of free roaming on those hotspots remaining
– T-Mobile’s SSID is now hidden/invisible and that you have to manually configure it for WiFi access
– The T-Mobile hotspot login option is a tiny icon/link on the AT&T hotspot login screen

Here’s what I don’t know/understand…

I walked into a Starbucks that I visited just a few weeks ago and was able to use the hidden “tmobile” SSID with the AT&T provided hotspot. I walked into the same Starbucks this morning and saw the visible AT&T SSID but could not use T-Mobile’s. And, I did not see a T-Mobile hotspot login when connected to an Access Point with AT&T’s SSID. I’m going to give T-Mobile a call in the morning to try to sort this problem out. But, if anyone has an explanation for what I saw, I’d appreciate hearing it.