Don't have lollipop (I have 4.4.4), but had some issues doing this, and thought I'd post my resolutions in case others are having the same thing.
First off, if you use the free SQLite Editor app (not the $3 one), you may not find it in the Apps section. (I didn't, anyway.) The database can also be found here: /data/data/com.android.providers.settings/databases/settings.db
Secondly, I was unable to edit the file directly. Permissions seemed set correctly, and SQLite Editor had root rights, but whenever I edited the db and went back into it, it was back to the original state. I used ES File Explorer (root) to copy the settings.db file from the above location to /sdcard/Downloads, edited the db, then copied it back to the above location. Rebooted, and now the quick settings tile is there. (Thanks to the Lollipop people who have been successfully using this method for a while now.)
I can also confirm, as has been mentioned several times, the actual capitalization is WiFiHotspot (not with the lowercase F, as it says in at least one place on the OP.)
Thanks to the OP for the technique!
EDIT: PLEASE NOTE, if you use the above "copy" method, you will need to set the permissions back to what they were before. I ended up noticing that I wasn't RECEIVING any text messages. I could send just fine, but could not receive. Couldn't figure out what I did. Did a factory reset, which fixed it...until I applied this fix again. Set the permissions back to what they were, and mine were rwx rwx rwx. That took care of the texting issue for me.