I think seemed like is an understatement. They hit you in the face will it. Mike tells Jimmy specifically that he "leaves the bag and I need you to see who he leaves it with" and he doesn't leave the bag. At this point Jimmy is the worst PI in all of history; only white guy in the place, wearing a suit and he follows him around the restaurant, literally, and he can't stop staring at him.

Then as soon as he dumps his waste leaves Jimmy starts digging through the trash?

The fact that Gus spotted Jimmy and called off the exchange is reinforced when Jimmy in his account to Mike says "he ate his food as fast as he could and left." And...ETA: Forgot about Gus going outside to see, and hear the whine, of Jimmy's car as he leaves.
This is a brilliant scene paralleling Jimmy's incompetence both as a lawyer and as a PI working for Mike. And yet he shows glimmers of genius: His law firm is thriving as a result of manipulating old people and he made a smart quick thinking move by dropping his watch as an excuse for digging through the trash. It's really a wonderful display of his transformation into Saul.