How to recover photos from a stolen iPhone's front camera?

Photos are stored in the Photos app regardless of the camera used to take them. If you were using iCloud Photos they are then uploaded to iCloud.

You can log in to https://icloud.com/photos on another device or computer using the Apple account from the iPhone, and verify if any photos were uploaded and you can download them from there.

If you were not using iCloud Photos or they have not been uploaded, there is no way to get to them. There is no remote access to an iPhone if that is what you are thinking.

What Phil0124 said with one addition: If you didn't use iCloud Photos, but you had Settings>Apple ID>iCloud Backup turned on, then you may be able to recover data. You should look here:

Restore your iPhone, iPad, or iPod touch from a backup - Apple Support 

“Restore” is what you do when you buy a new phone, so this safety, if you had it set, requires a freshly erased iPhone to retrieve the backup. You would need to borrow and erase a friend's iPhone, or buy a new iPhone to use your iCloud backup.