What do I do? How do I respond to this?

About 20 minutes ago, 3 teenagers came to my door (I'm a teenager myself.)
It was two guys and 1 girl, all about the same age. One of the guys, who did most of the talking, was saying that he was at the mall with his two friends and he lost his iPhone 5s and was tracking it on "find my iPhone," and it led him directly to my house.
He had a phone in his hand with the tracking device on it, and kept insisting that it was telling him it was at my house. I told him that I haven't been anywhere today, and that I surely wouldn't steal a phone. I have a phone of my own, I don't need his.
There's an alley way right behind my house with a strip center and it has a cellphone store, although I'm not sure if they're open on Sundays or not. The kid said he noticed it on his way over here.
I told him it was possible that someone could have been walking in the alley way and possibly tossed it into my backyard or my neighbors backyard or that it could be in the alley, even though it's locked.
I told him he was welcome to look around and that I would check my backyard, but that I didn't have it and I didn't know what else to tell him.
I was wondering if maybe his "find my iPhone," was accurate enough that it maybe could have brought him to my house while someone tossed the phone close by, or if it was all just bs? The girl that was with them kept staring at me, never taking her eyes off of me and was looking at me as if she didn't believe I was telling them the truth.

That iPhone feature is notoriously not accurate.

Sounds like somebody trying to rob you.

Find my iPhone is accurate… To a degree. The phone is likely in your neighborhood, not your house. You did the right thing by telling them what you did. I'm not sure I would have even answered the door. If they come back, tell them that you don't have it and if they don't stop knocking on your door, you'll be calling the police for harassment. Do it, too. They have no proof besides an app that's notorious for not being very accurate.

I would not let them walk into my house. They should have call cops and the cops should've done searching if that needed.

These 3 kids could have been a gang who will burglarize your house next day when everyone at work and school, and the house is empty, or may be they already pick something up, when you let them in. You never know.

Haven't you've been taught by your parents not to talk to strangers?

If they Really aren't lying and think that they are THAT close in proximity
to his phone then all they have to do is CALL THEIR OWN NUMBER,… And listern
FOR THE RINGING. You definitely do NOT let them in.