One of the reasons why, as a DM, I like the Passive Perception mechanic in 5e. It takes some of the thrill of a roll away from the players, but it gives me the tools to resolve these sorts of situations without tempting the players to metagame.
You can also summon scratch and he will find it for you. Apparently he even finds chests that don't have a visible survival check. But I can't confirm that because I never have him summoned.
Yup, it's an ability called "Find Familiar: Scratch" You need to have had a few interactions with him in the camp before the ability appears. I think it can be found in the "Common" section of your spellbook once you have it.
You also don't need to worry about him dying. You can always resummon him. But he is fairly useless in combat and other familiars are better.
You can also summon the owlbear cub, Mayrina's husband Connor, Us the brain creature from the nautiloid, 4 ghouls from the Necronomicon of Thay, a fairy from the broken moonlantern, the quasit Shovel. I think that's all of them.
What the hell?! I didn't know about this either! I guess it makes sense from a realism standpoint, but damn, that's good to know that its possible in game as well.