How to determine the voltage on the drain of a "hanging" PMOS
Looks to me that M2 is partially open, which means it conducts some current, while M1 conducts no current. This means that the only connection to Va is a weak pullup, thus Va will have +10V. 
You can think of it as a voltage divider, where M1 and M2 have are approximated by R_M1 and R_M2 resistance (R_M1 is almost infinite resistance, R_M2 is not). Then you can calculate:


  10 volt * R_M1 / (R_M2 + R_M1) = 10 volt   if R_M1 >> R_M2