I found this in the Errata and FAQ from April 2016.
Q. Odin: He provides +2 to Search Checks. How does this work?
A. Roll one die for the Search Check and add 2 to the result. So if you roll a 1, it becomes a 3.
This is correct. A search check is a single die, so a "+X" to a search check is added to a single die result.