You don't need hot water or soap for the ride home. You can clean it enough to stave off corrosion using nothing but the spit from your pie hole, oil off your dipstick, and a bar napkin.
Not cleaning a BP rifle before you get home isn't an issue. It's NOT CLEANING the rifle that's the issue.
One of my first muzzleloaders was a TC or maybe Lyman (kit gun?) Someone threw it together, fired it and never cleaned it. Hadn't even bothered to put any finish on the stock.
Bought it for next to nothing, pulled it down and got busy working on it.
Did the electrolysis thing on the barrel while I was working. Got a big tub, filled it up and hooked a battery charger to it and let it work all day. Got the corrosion out of it but the barrel was pitted REAL BAD.
Finally got after the bore with a hone the best I could. Got it pretty smooth but not enough "I thought" to get a patched ball down and seated. Still got it !! Saw it the other day, sights and all.
Ended up setting the barrel aside and installing a .32 Green Mountain replacement drop in barrel.
Fired it a few times, cleaned it and set it aside, never to be fired again. Posted it For Sale but no takers that didn't want it for next to nothing.
Electrolysis, interesting process.