(OP: i dont think OID will do what you want)
from what i can see , you need to snmp WALK: 1.3.6.1.4.1.25053.1.2.2.1.1.2.1.1.3
when i walk that, i get 216 x OIDs , each with a 1 or 0 (ie status connected or disconnected). this lines up w my ZD having 216 APs, and about 6x of them are curretnly disconnected.
however the issue becomes how do you monitor 216x OIDs via a snmp device (like PRTG or MRTG).
what i do is monitor:
1.3.6.1.4.1.25053.1.2.1.1.1.15.1.0
which is generated on/from the ZD and returns a # for current connected APs to the ZD (so if you see a drop then you know some APs are missing/disconnected).
its the opposite of waht OP wants, but can accomplish the same thing. (if you use PRTG you can use sensor factor to subtract this value from a static # you input, of your total active aps, ie in my case, 216 - = # of disconnected (or 0 if no disconnected aps)