Kinda reminds me of the Thai restaurant in Sacramento with the prominent $10 minimum notice. The costliest lunch was $6. I ordered a beer; my tab shot up to around $8 (pre-tax/tip). I had every intention of rounding the bill up to $10 even via tip.

I put the bill and cc on the table. The previously attentive staff pointedly ignored me - to the extent where I would have had to either yell or get up and go after them. The times any were nearby they made efforts to avoid eye contact. I waited and waited.

Got up, put on my jacket, etc. slowly, picked up the cc and made my way in leisurely manner out the door ... right out to the sidewalk. No response.