Is There a Squirrel?

I heard Xander call for help today. I was in the middle of helping Venice with something, so yelled up to Xander that he had to wait a few minutes. A few minutes later I walked upstairs and called to Xander. I hear a muffled, "I'm in the closet, Mom." I opened the closet door and asked Xander why he was in there.
"Because, there's a squirrel!" lower lip trembling.
"What?"
"I saw a squirrel."
"Where?"
"It went under the couch!" he says with a touch of panic in his voice.
"Could it have been a mouse?" I ask.
"No! It was a squirrel!"
So, I looked under all the couches in the room, couldn't find anything. And am left wondering, how long do I look after hearing son say, "I saw a squirrel run under the couch."