From my perspective, he should definitely make an effort to show gratefulness for your gratuity. If he has the monetary means to do so that is. If he has no source of income, I hope he is making a valiant effort to find one, because your gratuity cannot last forever.

The trip was something he suggested

This, without question, should have been paid for in full
by him.
That is only my opinion, but I would never even think of suggesting a trip of any sort, without fully intending to pay.

Since I agree with you 100% that this is a total slap in your face, I'm upvoting this 100%

Much love,
@futuremind