Adam,

Given the widespread use of such radioactive sources, not just for medical purposes, it is remarkable how few incidents have been reported.

Mexico is relatively stable unlike some places.

Years ago there was a YouTube clip IIRC of a post-Soviet era recovery of radioactive sources, the crew had very, very basic equipment - long handled ladles - to scoop up the containers. At least Mexico has "Uncle Sam" who can help with more than ladles!