My sushi place used to add this side vegetable to my sushi boxes, but stopped adding it over a year ago, however i loved that stuff and am now wondering what it may be called so I can buy it on my own. It was some green stringy vegetable(seaweed?) that was served in a small nested ball, and if iirc it was mixed with some sesame seeds. 

yeah, seaweed.  ask them about it

Sounds like seaweed salad 

Thanks! Googled seaweed salad and apparently what I'm looking for is called wakame.