Missing iCloud backups for specific days on iPhone

Hey everyone

I travelled a month ago, my iCloud and everything was syncing and all was well. I then lost my phone, and upon losing it, I saw that on my cloud, there is a 3 day gap, where there are no photos backed up. There are photo's take after the 3 days, but not these particular days.

What could cause this? the iCloud space was fine and updated, the were back ups afterwards but the three days are totally missing.

what could be the cause?

[Re-Titled by Moderator]

Original Title: iCloud back up issue