I do agree that it is confusing and wrong of the police to just ignore it, but what can they do? What evidence does the police have that would indicate that this is not his (the taxi drivers) phone?

I say it's my phone.

Officer says to me, prove it.

I enter the phone password, point out that it's full of photos of my children and wife, that the "Home" number calls my house, etc. etc.

Phones are probably one of the MOST identifiable items that you own.

Serial number? IMEI? Calling the cellphone company to see who pays the bills?

They have endless resources when they are motivated - if an off-duty cop or their spouse had been pickpocketed this would have been resolved in 30 minutes flat.

So you mean a he said/he said case? I'm pretty sure they investigate those all the time (most assaults would be this way) and have even less potential evidence than they would with a phone.