The throwout bearing is already sealed, so would be aftermarket throwout bearings. You probably got mud in everything else, like between the pressure plate and clutch disk. Once you get things working again, learn to never step on the clutch when you're in deep mud or muddy water to prevent this from happening again. If you get stuck, don't step on the clutch. Kill the engine, shift into 1st without stepping on the clutch. Then start the engine while in 1st gear and you'll be moving again. This of course assumes you already defeated the clutch interlock by installing a fuse into the #20 position on the fuse panel per the instructions in your owners manual.