How do I find a trigger function that is raising notices?

Greetings!

I've got a query that is behaving strangely, but that's not the reason for this question. The update results in a trigger being fired, but I don't know which one. I thought I disabled all of the triggers on the table being updated. So, I wanted to find the trigger function that contains one of the words in the notice message. A long time ago, someone told me I can search for a function containing a given word using this query:

Select * from pg_proc where lower(prosrc) = '%<target_string>%'

But that's not returning any rows. Is there a different table that contains source for trigger functions? How can I find out what trigger function raised these messages?

Thanks very much!

RobR