WiFi Network Name and Password Changed Overnight. Was I Hacked?

I rent my router/modem from the local cable company through which I have internet service. My partner was connected to the WiFi last night on her phone with no issues. This afternoon after work I attempted to connect only to find the network was no longer there! Instead there was a network with my last name that I could not connect to using my password.

I called the cable company and they said they have no idea why this occurred or any record of anything else atypical. The only additional information they had was that the password had been changed to "Welcome!". They said if this happened again to contact local authorities because it might be a hack.

Do I have reason to worry it may have been a hack? It seems bizarre that a hacker would change the network name and password. Moreover, the fact that the password was a standard initial password like "Welcome!" seems to indicate that something was reset, either on the company's end or with the modem.

(Also posted on r/techsupport)