I mean, yeah maybe the system roasted just for the sake of the story, but this manga actually address it and makes his problem look TOO SILLY TO GRUDGE ON!
I think there are plenty of simple ways to explain this — like how, after dropping his phone into the sewer, Tanaka might’ve learned his lesson and bought a backup phone, or maybe he went back later to retrieve it, or it could’ve been Sato’s phone and he just logged into Tanaka’s account… Either way, I think this is just a small, acceptable inconsistency xD