Has anyone noticed?

[inquisitor]

Unfortunately few modern phones including all Android phones I owned so far allow a band selection or even have a field test mode that would reveal the used frequency band. Interestingly the most restricted smartphone of all, the iPhone, has a field test mode which shows the number of the current radio channel, which enable identification of the current frequency band. Just dial *3001#12345#* to enter the field test mode and find the "AR FCN" (Absolute Radio Frequency Channel Number) somewhere under GSM Cell Environment or UMTS Cell Environment (don't have an iPhone so can't provide more detailed instructions).
And these are the AR FCN for the GSM bands:

GSM850 128–251
GSM1900 512–810

GSM900 1–124
EGSM900 0,975–1023
GSM1800 512–885

Obviously GSM1800 and GSM1900 have overlapping channel numbers but you can rule out one of these bands as you usually know on which continent you are.

For UMTS channels there's an overview at UMTS frequency bands - Wikipedia, the free encyclopedia