Knowing what mod it is would help a lot.
But I have a suspicion that it is one of the Istick series.
However, if you have a set of needle nose pliers, you could try to gently pull the button out.
Last resort if you can't return it, you could try Engineer's Thump.
Put some padding on a table and "Thump" the device on it in hopes that it dislodges the button.
Like I said, last resort!