Yes, it is possible for files and folders to be accidentally deleted from SharePoint or OneDrive, especially when using the OneDrive sync client. This can occur when a user deletes a file locally in a folder that is synchronized with SharePoint or OneDrive, which then synchronizes the delete operation with SharePoint Online, moving the item to the recycle bin.
To determine if the deletion was accidental or malicious, you can check the Deleted By field in the SharePoint Online or OneDrive for Business recycle bin. This field indicates which user performed the delete operation. If the user listed in the Deleted By field is not the one who intended to delete the file, it may suggest that the deletion was either accidental or caused by a local application or process, such as virus protection software that may have quarantined files.
If you find that the deletion was not intentional, it is advisable for the user listed in the Deleted By field to review their computer to see if any local processes moved or deleted the item.
For further assistance, users can refer to the SharePoint Community for additional support.