Pellets are very finicky at times. I would guess that with the cold weather, even being put in a truck the powder drew moisture. Inside of vehicles can be a very damp place. Especially if you drag snow into them on your boots and run the heater at all in the truck. Have you ever got in your truck and noticed the inside of the windshields all frosted up? The same would happen in your barrel.
I would push the pellets and projectile out at the end of the day if you get no shot. Or you can pick out a spot and shoot it out. But anyway, push the powder and projectile out and save that for a range day. Then take an alcohol patch and swab the bore area. Then a dry patch. You could even run a light oil patch through the barrel as well if you really want protection. Then, before you start your hunting the next day, patch the barrel with a dry patch and then load it.
What you are doing is taking the moisture factor out of the equation. You are basically starting each day with a clean dry rifle. Years ago when we hunted with traditional rifle, we would shoot them off and then patch them clean for the next day. With these inlines and the fact you can pull the breech plug, it is so easy to reload them clean the next day.