the div id is created based on the map, if you create another map a new JS file will be created using the namer google_javascript/wagmp_map_3.js which will use the div ID wagmp_map_3
my guess is that you added a second map to the page at one time which generated the wagmp_map_2 div, then deleted it from the page but deleted the wagmp_map_1 instead of the wagmp_map_2 div.