I've never heard a throwout bearing called a thrust bearing. A thrust bearing is the bearing in an engine that prevents the crankshaft from moving fore and aft.
My 300E with manual transmission rattles slightly when clutch pedal is released. There is no tension on the throwout lever at that time, so it is free to rattle. There should not be tension on the throwout lever, if there is, the bearing is contacting the pressure plate and spinning. The throwout bearing is only packed in grease, and only designed to turn whenever the clutch pedal is pressed. If the bearing rides on the pressure plate all the time, it won't last long. It's just as much trouble to replace a TO bearing as it is to replace the clutch, at least 98% as much work. Replace the pilot bearing while you're there. Yes it has one, all manual transmission cars have a pilot bearing or bushing.
'84 Euro 240D, 523K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in