Although my laundry has been dried in the drier, my sims get the sad because their laundry is 'wet.'
Edit By Crinrict: Added Tag to Title, Adjusted Title
Ideas
Sometimes (like in real life) the drier doesn't dry the laundry all the way. When you pull the laundry out, hover over the "put laundry down" option for a second, (even though you probably aren't going to do that,) and it'll show you the status of how dry the laundry is. For whatever reason, hovering over the "put laundry away" option does not show the status of how dry the laundry is.
This is the same for the washing machine. Hovering of the options will show you the status of how clean the laundry is before you stick it in the drier.