There is no log for changes in the Lansweeper web console. If you are unsure why assets get deleted, we recommend that you review the settings under
Configuration\Server options, section
Asset Cleanup Options. Possibly assets have been deleted automatically because they weren't scanned for some time or computers have been disabled/deleted in Active Directory.
Open
Assets and filter for the asset you are missing in order to see if they have been put into a non-active state.