Mine also has disappeared after only being there about 12 hours so I hope it comes back. It didn’t have an expiration until April 9 and I had planned to shop tomorrow.
I also had this bonus appear, then disappear. But last time I signed up for it and it would be nice to have a bonus for this for users who already signed up.
But in regards to those who havent signed up, you can still get credit. Just put that signup code ibotta2021 when signing up and it should still credit you. Because that's what happened for me last time, I signed up and the offer dissapeared but I still submitted a reciept with a box top and was credited by ibotta.