LongHorn Steakhouse review: customer service

I ate at Longhorn with a couple of friends, my husband, and my 1 year old son last night, September 28, 2019, at around 8:30 pm. We stayed until closing to catch up with our friends. When we left we didn't realize my child has left his sippy cup until we got to the car. Since we were still at the restaurant, I sent my husband to go get it but the manager on staff wouldn't unlock the door and said he would look for it. Someone had thrown it away. I called this morning just to be sure and the manager that answered said that it had probably been thrown away. We had already eaten dinner yesterday so we only ordered an order of Mac n cheese and an order of chili so out total was around 15 dollars plus I left a 5 dollar tip for our waitress. The cup itself was 15 dollars so I feel like they should have at least put it in lost and found.