Using Underscore Method 'find' on a Backbone Collection

I'm trying to use the Underscore method 'find' on a collection but it is not giving me the results I expected:

I have a base model with no defaults, and a default collection. The models in my collection have only two attributes: tranId(a guid as a string), and perform(a function to perform).

I'm trying to find the item in the collection that matches the tranId that I pass it...

    var tranId = "1a2b3c";

    var found = _.find(myCollection, function(item){
        return item.tranId === tranId;
    });

Found is always undefined, even though the debugger shows that my collection does, indeed have an item in it where tranId matches my variable. I am unable to set a breakpoint at the return statement to see what item.tranId equates to. I have also tried this...

    var found = _.find(myCollection, function(item){
        return item.get('tranId') === tranId;
    });

But, same thing. 'found' is always undefined. What am I doing wrong here?