Rebuilding or reconnecting Outlook autocomplete cache

either in exchange 2013+ or Office 365.

If you created a new outlook profile, I'm sure you've had complaints about 'contacts' missing. AKA the autocomplete cache.
This used to be stored in the NK2 file, stored in user\AppData\Roaming\Microsoft\Outlook\ rename as the current profile and you're done.
Microsoft holds this data on the server now, which is nice, BUT, what if you just migrated to Office365 like you have to? Because Microsoft is mother, Microsoft is father. Yes master Microsoft, I will do whatever you say. I don't need servers anymore, all must be cloud. Thank you.

Users\user\AppData\Local\Microsoft\Outlook\RoamCache\ holds a .dat file of your autocomplete
Its a super cool file name Stream_Autocomplete_absolutejibberish. It really makes it easy to find out what the new one is and what the old one was... Not.
Its easy enough to figure out which is the new autocomplete dat though, the one that's a KB and was made today, that's the new one. The old one is easy to find too. The one that wasn't made today, and has a lot of KB.

Close outlook, copy the old dat to a different folder (incase this all goes south and you have to try again, which I talk about below)
You'll want to change the old .dat filename to the new .datfile name. The file with the KBs will have the new file name. I hope that's clear... I'm reading it now and its not.
Copy the file name of the new dat, and delete new dat file. Den copy da new dat name to da old dat file and save dat shit.
Open outlook and take a look, all dat autocomplete is back.


Weird shit:
So I would do these steps, copy the new name, delete the new file, copy the new name to the old file, open outlook and watch as the Autocomplete file shrunk from 1000kb to 60kb... remember that step I said about copying the old autocomplete to a new file? Bet you wish you did that now, don't you. Close outlook, rename again and it should work. No idea why this is happening, but I seem to have to do the process twice.
Close outlook, rename, open outlook, close outlook, rename, done.