By accident, factory data reset on wrong phone. Still possible to recover photos? -Is there a way to recover at least some of the photos after factory data reset on S9 +?
-Background: My sister gave me a Galaxy S9 + as a birthday present. Wonderful birthday party, took great photos with my new toy. But I was surprised because for her, S9 + is an important expense. Next day, I asked her if she wants my S7. She said yes. I didn't think and performed factory data reset on the new S9 +. All photos of a great evening gone.
Yes you can try the following; 


Download and install Android Phone Recovery on your computer. Then connect your Android phone or tablet to computer. 
Run Data Recovery software for Android. Enable USB debugging on your device, the program will automatically identify your Android device, and then click “Start” to search for lost files.
After scanning, all found files will be listed. Preview and check to recover data after factory reset Android. 


More information can be found here