how do I access my iMac if the mouse is missing/not working

I just purchased a iMac w/ a Magic Mouse 2. I have come from 6 years of using a MacBook Pro with a mouse and the track pad.

After setting up my iMac with the mouse all was good. The set up was done at the Apple Store.

This afternoon I misplace my mouse. I was unable to use the iMac.

Is there a fine my mouse an if there is how do I use the Mac to find it?

I called the store and they said I should purchase another mouse or a track pad as back up.

Is this the only way to access this computer, if I don't have a Bluetooth MOUSE OR A TRACK PAD I'm stuck.

This must have happened to someone other than me, what are the suggestions please.

how do I access my iMac if the mouse is missing/not working