Why did my bunny just suddenly not want to eat hay but still eats his treat?

My bunny is almost a year old now and he’s had GI stasis before, I’m very worried that he’s showing symptoms of it again but what I found odd was he’s still eating his treat (apple)
I accidentally ran out of hay yesterday and gave him plenty of his pellets n a big carrot for him to pull through until the morning.
It’s in the afternoon now and he’s not touched his hay and I’m getting worried

How does his stomach feel like and the droppings. Does he act a different way.

Can also be he’s stuffed with everything before or waiting to get something more yummy. If he’s had no droppings and not eating I would really worry and take him to the vet directly.

You can also massage the stomach and give baby gas drops, if he have gas. If the stomach make some gurgling sound and seem to be filled.

An entire carrot is loaded with sugar and should not be fed all at one time. A 1" slice is the max per day. That alone could send a rabbit into GI stress.

Suddenly feeding a large amount of pellets could have the same effect.

Too much of those rich foods, as Hermelin said, could have made him really full (and/or spoiled for more rich food).

In the future, bear in mind that hay is the one constant that should never run out. If he runs out of pellets, no big deal. He could go a few days without pellets ( or fruits or greens or veggies), but hay is the one thing to never run out of.