Show your baby a toy they like and let them hold it briefly, then take it back gently.
While they are watching, cover it with a cloth — leaving a corner of the toy visible the first few times.
Wait. Give them time to reach. If nothing happens, lift the cloth yourself and show it with delight. As they get better, cover it completely.
Searching for a hidden object is object permanence made active: the baby must remember what was there and act on that memory. Leaving a corner visible creates a solvable first step, which is what turns a puzzle into a success instead of a shrug.