One of Google Pay's more useful features is its ability to store your transit passes, saving you from having to carry physical tickets. However, a recently updated Google support article now warns that, unlike any other item in Google Pay, your transit passes aren't stored in the cloud. You can permanently lose your transit tickets if you lose your phone or simply uninstall the app.
Apparently, adding transit passes to Google Pay only adds them to that device—they're kept locally in the Google Pay app. Uninstalling or even clearing app data is enough to lose your tickets, and there's no way to restore access other than purchasing a new pass and hoping your transit agency gives you a refund on the lost one. There is a function to transfer passes to a new device if necessary, but the feature must be enabled by your transit agency, and it does nothing to help an inadvertent loss of data.
These clumsy processes may be a measure to prevent multiple people from using a single pass (for example, an unlimited monthly pass). Rather than implementing an elegant solution to ensure the pass is only active on a single device, it seems Google has taken the easy way out by keeping transit passes entirely local. The situation is especially odd as Google promised back in June that passengers could soon use their passes even if the Pay app was not installed in the first place. Now, besides having not delivered on that feature, users can't uninstall the app at all for fear of losing access to their transit pass entirely.
If you have lost your tickets due to losing app data, see Google's support page for instructions on recovering your ticket number. You just have to hope your transit agency has some sympathy.