One of the 'tricks" is that Rhapsody is not always listed as Rhapsody. I've seen Rhapsody DR2 listed as OpenStep 5.2 (even though it is version 5.1) and Mac OS X Server DR2 or Beta.
For those of you who are interested in the version names and numbers of the discontinued Server line, here is what I have so far:
Rhapsody Developer Release: ? : version 5.0
Rhapsody Developer Release 2: Titan1U : version 5.1
Rhapsody 1.0 (never released): ? : version 5.2
Mac OS X Server 1.0: Hera1O9 : version 5.3
Mac OS X Server 1.0.1: Hera1O9 : version 5.4
Mac OS X Server 1.0.2: Hera1O9+Loki2G1 : version 5.5
Mac OS X Server 1.2: Pele1Q10 : version 5.6
That should help with looking for them. I'm still looking for Rhapsody DR (both Intel and PPC) to round out my OS collection, which is why I still come across DR2 from time to time.