I was there. So the source was right I was in the northern part of the parking lot. Did not see the toilets 100m down. But thanks for pointing out the toilets south. How far left and right am I required to check so I can use survey as a source and what source would I use instead if I am there but did not check 100m further south?

Added the toilets in the south under changeset: 118969911.
Did it on the phone, will check at home using JOSM.

Yes you are right it is on the other side of the car park. Will undo the change, than move the node into the right spot.

Oh, sorry. I checked the spot and there was no toilet block there. Have not checked the south of the car park. Edit was made through street complete. Will check in 10 min and undo and move. Thanks for the hint.