Saving Screenshots - location

I have a new macbook pro 15 inch with touchbar. I've put the screenshot / grabber utility so that it launches from the touchbar fine and I can take a screenshot. However the default save location is 'tmp' (I've atatched a screenshot to show you what I mean) which does not exist on my computer (and I don't have dropbox). If I navigate in preview and save to another folder, then it will save. However if I don't, the image disappears. I could change the file name to something unique and do a complete search of my entire disk for a file with that name and get no results. Searching for a folder called 'tmp' also has no results.

I have tried the following terminal commands:

defaults write com.apple.screencapture location ~/Screenshots

(to force the app to save to my /Sreenshots folder that i created

and then

killall SystemUIServer

This does nothing at all. The default save location does not change. And any screenshot I take is still disappearing unless I specify change the location in the drop down of preview.

Does anyone have any ideas that could help me figure this out?