Does the FBI ever contact a person by phone or text without seeing them in person?

Well, check this out. A colonoscopy is a procedure to examine the inside of your colon (intestine) with a scope. A scope is a flexible tube with a small light and camera on the end.

You should find the answer there. 

Of course it's possible, but they would never send an unsolicited text. And regardless of the reason, you're supposed to get that person's name & badge #, then VERIFY it's genuine before you say anything.

No they don't warn people if they're coming after them.

If you mean something like telling you there is a warrant for your arrest then no, it's a scam.

It's like when some guy with an Indian accent called me the other day saying he was calling from Medicare-- um, no you're not.

Only the ones who want your credit card number.