Google accidentally deleted or marked as spam some users messages. The issue occurred between January 15 and January 22 and is now fixed. Not all Gmail users are affected by the bug and not all users affected by it. Google says the bug was introduced during a software update on a few platforms – its iOS app, mobile browsers and the offline version of Gmail and not everyone is affected. If you use the Gmail app on your iPhone or iPad, it might be sensible to check your Trash and Spam folders before Valentines Day.”]
Source: https://grahamcluley.com/gmail-ios-users-told-check-trash-spam-feb-14th/