Well. That sucked.
So I just called the number that I have saved for him (from the phone's memory, so no mistyping.) Someone picked up, and it sounded like my dad... so I took a deep breath and say, "Hi Dad! This is guilloche! Happy Birthday!" - there was an awkward pause - and the voice said, "uh, wrong number."
Uh. Um. Er?
I said, "This isn't <FirstName> <LastName>"? Because it sounded like him... and the guy said, "No."
Me: "Oh, I'm sorry. Bye."
So, now I don't know if my dad is dead... or just decided to change his phone number and not let anyone know. My sister hasn't talked to him since Dec/Jan too, and my brother hasn't talked to him in ~6 years. What the heck?
I guess I did my part. My number hasn't changed. My email hasn't changed. He is 100% capable of getting in touch with me at any point.

Kinda hating T for encouraging this.