I think you have very little chance of finding it, but here goes:
Your best bet is your Google account (I owned this phone and don't recall every having an HTC account). If you had the service enabled you can use Google's
Find My Device website to locate it (it would have been called something different on a phone as old as the M7, I think "Android Device Manager", but it's the same service and the same website will work). The catch is that this will only work if the phone is connected to the internet, logged into your account and has location enabled. Unless all 3 of those conditions are met this won't work. So what are the chances that a year after it was stolen someone is keeping the phone charged-up and powered-on and still with your account on it (i.e. without doing a factory reset to get past your lockscreen)? This phone does not have the modern factory reset protection system, so someone could reset it and then put their own account on.
I think the chance of this working is basically nil, but at least it won't take long to try.
If you had Google Location History switched on you may be able to log in to your Google account and find where the phone was last seen (i.e. last location update).
The catch with all of this is that Google will disconnect devices from your account if they haven't been used for some time (I can't remember whether it's 3 or 6 months, but it's less than a year). Using them again will reconnect them, but that's not likely unless someone has reset the device (in which case it won't reconnect to your account anyway). So chances are none of this will work anyway. The Google Location History is your best bet, but since I keep that turned off myself I cannot check whether it will say anything about my M7 (which has been disconnected long enough that it no longer shows amongst my devices in my Google account).
The other consideration: did you report the phone as stolen to your service provider? If you did they will have blacklisted the IMEI, meaning that it will not be able to connect to any cellular network (not just yours: in sensible countries the providers share blacklists).
I'm afraid the real lesson here is that if a file is important you should never have only one copy, and that the backup should always be on a different device from the original. This is particularly true with phones, which are more likely to be lost, stolen or damaged beyond recovery than most other storage devices.
