How did Jay Time Travel back to the Present?

Im probably really dumb and missed something. But with this recent rewatch. The ending and post credit scene of the movie doesn't show Jay finding another way to travel back in time to the present. All he did was cross out the little phrase in the whiteboard and leave. Did he find another Orbitz bottle or some other source of energy in order to power the flux capacitor?

This is a very small nitpick, but it's been rattling in my brain ever since I saw the movie a month ago. I need someone to answer it, please!