Contacts disappearing from iPhone; no Contacts showing on iCloud

I’m trying to resolve 2 seemingly linked issues for my wife - some insight and assistance would be immensely helpful!

issue #1: certain contacts have disappeared from the Contacts on my wife’s iPhone & iPad. So far 2 have been clearly identified but I would guess there are others, just not apparent so far. The first is a very long term contact for whom a full record (name, address, emails, mobile etc. etc.) was held: this person now only shows up when searched for & their very limited contact info is showing as ‘found in apps’. The second person is a new contact whose mobile number and first name were held: text messages show with only the senders number showing, not her name.

This suddenly happened late last week and, as far as I understand it, without any action on my wife’s part. Any idea why, how to retrieve the data & how to prevent this from recurring?

issue #2: despite having iCloud backup it appears Contacts is not being backed up & there is no Contacts tab when accessing iCloud via the net. If there had been a backup I assume we could have restored Contacts on the iPhone from it. Is there a setting missing from her phone? Is Contacts unavailable on iCloud? Can anyone explain what’s wrong & how to resolve this?

FYI the phone is an iPhone 6s Plus / iOS 15.7.5 & the iPad is a 9th gen/iOS 16.4.1(a).