The first question is... ARE you using layers. If you're not sure, then probably not. I've never worked with layers myself, I'm not even sure if it's possible in CoD2Radiant.

I meant "check in Radiant to make sure you didnt rename the trigger or accidently delete it" that part. Because the error says that 'trig' is not defined. You did define trig just a few lines before, which leads us to the conclusion there is something wrong with the trigger brush. Either it's not there anymore, or there is a typo in the targetname key/value pair.

the trigger is undefined because it cannot be found for some reason.

check in Radiant to make sure you didnt rename the trigger or accidently delete it, or maybe accidently disable the layer the trigger is in if you are using layers.
if it is disabled (set to ignore during compiling) the layer will have a red circle with line on it, like a No Entry sign would look like.