Terry,
I don't have a manual for the 95 Mercury, but I was able to find this.
http://www.trademotion.com/partlocator/index.cfm?action=selectTree&CatalogID=2&siteid=213671 I hope this link works for you, because it has the prices for mirror glass only. Must be a FRU. I know in most cars the glass just pops in and out. You have to be very careful though not to break the glass or the mirror housing.
Seems kinda strange that someone would just take the glass off the car. I am sure you have done this, but check around the neighberhood for the car. Yyou should do it quick so you could look for a broken mirror if they haven't switched them already.
Good luck.