I have obtained a copy of the current version of the database of the WhatsApp instance running on my phone. I can see that deleted messages do not show up, and that there are missing IDs corresponding to those messages.
I have not checked, but I assume that the crypt12 backup files on sdcard0 do not contain these messages either. These backups are generated daily.
I have seen plenty of apps that claim to undelete WhatsApp messages. I can understand how a message that is not part of the current database version can be recovered if it is present on one of the backups.
However, is it reasonable to expect these apps to recover messages that have been removed so quickly that they have not been backed up?
Does Android allow some sort of low level hardware access to try and find data that has been marked as deleted, just like data recovery tools such as testdisk?