Nope.
That depends. Were they simply deleted or did you restore the phone or something? Also, were the photos on the SD card on in the phone’s internal memory?
Regardless, you could try plugging the phone into your computer and using some photo recovery software. I’ve used this one in the past, though I’m sure there are plenty of other (better?) options out there: filehippo.com/download_file_recovery
I guess he was referring to the HTC cloud storage, not the actual phone, since he said “from HTC”, not “from my HTC phone”.
Doesn’t Google automatically backup photos on Android phones?
Depends on your settings.
OK, makes sense.
Every time I take a photo a get a notification telling me that the photo was automatically uploaded to Google +
I guess I must have downloaded Google + from Play Store. Or, maybe it came as an add on to the Gmail account I was required to open when I bought my first Android device. 
It’s entirely possible that was turned on by default as soon as you logged in with your Google account (which of course you have to do on Android devices). They’re very keen for you to sync things as much as possible. I seem to remember switching mine off. Anyway, you bring up a very relevant point and it would be well worth checking if the photos had indeed been automatically synched with her Google + account.