Perhaps it's just me, but I cant see why JP would be texting KD just to check if he had finished giving a pal a lift home.
I think they already knew, at this point, that they were going to store some dodgy stuff for NM. Proving it however, is another matter.
She may have worried about him being caught skiving off from work. A friend of mine used to do this occasionally, there would be two of them on the night shift with nothing much to do, and they would take it in turns to go home! I always felt it was a stupid risk to take as they would have been found out very easily.