I had a couple of items on my Walmart IB list that I took a picture of when I added just in case of missing credit. I have not used them and now they are missing from my list. My pickup is tomorrow and I don't know if I should delete the item from my Walmart order.
On occasion, I have had the same issue. It seems to happen when I have a large shopping order. I now make it a habit to keep a detailed list of any deals I plan to get and the max quantity allowed. for instance 5 sm size yogurts at 25 cents a yogurt. Then I try to keep all the deals together on the conveyer belt at the store. Since that store is "Linked," I also request a paper receipt with large orders. It helps in case I need to take a photo of it. When the customer service asks for the information about the deals, etc, I have it before me.
My understanding is the rebates are as of the time you place the order. If they were in Walmart Grocery Pickup & Delivery when you placed your order (and you had selected them), you should get credit for the rebate.
If it doesn't show up when the rest of your rebates are processed, I would open a request and include your picture showing it was there when you placed your order. Ibotta usually will credit your account. Just be aware it could take several days to get a response.