Weird hotspot password on iPhone after it was replaced by Apple

Solution 1:

iOS auto-generates a hotspot password by default, mine is a word followed by four digits, just like yours. I suspect that the hotspot password just isn't backed up, so the new phone created a new default one.

It's not an issue really, just replace it with whatever you want. If you want to keep the old one to avoid re-entering it on your devices, but don't remember it, you should be able to find it by going into Keychain Access (Applications > Utilities) on a Mac that connected previously. Double click on the entry corresponding to the hotspot name, and there should be a checkbox for "Show password".

Solution 2:

If you use encrypted backups, your backup will store your passwords (email etc, including the hot spot password). If you do not use encrypted backups, you need to reenter all passwords, including the hot spot one, which will be reentered by a random one as explained by CanuckSkier.