So, as the original poster, what did YOU mean by "popup"?

A) You filed an IFR flight plan but departed VFR and then, in flight,
contacted ATC to activate your flight plan

or

B) You filed no flight plan prior to takeoff. You departed VFR and
then, in flight, contacted ATC requesting an IFR clearance.

--
Cheers,
John Clonts
Temple, Texas
N7NZ