i just found a bug on survey maps. looks like that if someone for some reason don't collect all the materials from one map, the next time you get a map for the same location you only get what you left from the previous one and lose the map.
for example, by mistake i didn't collect one item from my last blacksmith survey, and now that i got another map for the same location i was only able to collect the one item i left from the previous one and the map was removed from my inventory.