A Hogle Zoo sea lion is recovering from an unfortunate encounter with a sock.

The zoo posted on Facebook that its “beautiful male sea lion, Diego, puked up a toddler’s sock Monday morning.” And that’s a lot more serious than it might sound — it could have been fatal.

The animal became ill on Sunday. “His keepers said he lost interest in training and even puked up blood,” according to the zoo, and he didn’t start to recover until Monday when he was able to vomit out the sock.

“We are extremely relieved he was able to get the sock out and is back out swimming in Rocky Shores,” the zoo posted, advising zoogoers that “animals can die from eating foreign objects.”

“PLEASE keep very careful track of your belongings near animals’ enclosures. Watch those little toddler socks, gloves, flip-flops, phones etc. And please, if you do drop something, please tell someone! Do not feel too embarrassed to let us know. We can retrieve the item if we know about it.”