Reconnaissance aircraft vs. Stealth aircraft

We often default AWACS, AEW as A50, KJ-2000, E-3, E-2 can detect the F-22 or F-35 through RCS, however, reconnaissance planes, ELINT / SIGHT there that may change as better

P-8, RC-135 or Tu-124R are capable of detecting the F-22, F-35 through RF signals

Most probably, among the weapons systems of interest there were also F-22 Raptors performing “kinetic situational awareness” tasks over Syria: the Tu-214R alongside the Il-20 Coot and other ground-based radars might have collected intelligence data needed to “characterize” the F-22’s signature at specific wavelengths.
http://theaviationist.com/2016/02/29/job-done-russias-most-advanced-spyplane-is-returning-home-after-deployment-in-syria/