One Dollar coin

So, a girl walks up to vending machine with the intention of buying a snack...
'a dollar bill' is inserted in...
'oops! my favorite cookie isnt there' says she...
'return the money' button is hit...
'Ding'- a dollar coin falls down...
'a dollar coin'- it is the first time she is seeing one ...
'...' - I don't know the word for that expression ...
here's my comic sketch for that... :)