Yes a jammer will jam any radio communication, not just Moteinos.
The radios have a capability to read the RSSI as a means to detect interference. The send function already has that check. However if you need to detect jamming then you might need to build a more complex algorithm for that purpose.
Another way is to use another channel or use a FHSS technique for communication. Even so a jammer that jams the whole 915 spectrum could cut communication but in general it's fair to say that it would take a very high tech thief to do that, the kind that would break into Louvre not at your house