I don't think an automatic iCloud backup would have replaced the photos on your iPhone. The important distinction is between iCloud Photos and iCloud Backup.
If you had iCloud Photos turned on, your iPhone and iCloud were being synced rather than iCloud simply keeping a separate backup copy. That means when you deleted the photos from iCloud on your PC, those deletions would eventually sync back to the iPhone as well. An iCloud Backup doesn't normally restore an older photo library over the current one. Photos already synced with iCloud Photos aren't included in the normal iCloud Backup.
Before trying any third-party recovery software, I'd check these places:
- Photos > Recently Deleted on the iPhone.
- iCloud.com > Photos > Recently Deleted.
- Your PC's folder where you downloaded the photos — make absolutely sure the downloaded originals are still there and open correctly.
- Any other computer, external drive, Windows Photos/iCloud Photos folder, or backup you may have used.
- Settings > [your name] > iCloud > Photos and confirm whether iCloud Photos is currently enabled.
If the deletions happened within the last 30 days, Recently Deleted is your best and safest recovery option. Apple normally keeps deleted iCloud Photos there for 30 days. There is one important catch: if your iCloud storage was already over its limit, Apple says deleted photos may be removed immediately rather than being recoverable from Recently Deleted.
I would not install random recovery programs from sites such as Taptweak or similar sites yet. They aren't necessary to determine what happened, and some recovery software can make promises that aren't realistic.
If the photos aren't in Recently Deleted and the originals aren't on the PC, the next question is whether you have an older iPhone/computer backup from before the photos disappeared. Don't erase or restore the iPhone yet,