In Plain Sight is the eighth episode of the second season. It was released on 18 November 2005. Data from a meth lab explosion reveals a photograph that triggers memories for Charlie and puts him at loggerheads with Don, who's focused on tracking down the drug dealer who set off the explosion that killed one of his agents.
The image comes from the concept of hiding in plain sight, one of the primary tenets of prestidigitation, and many forms of con. Its successful execution often requires high levels of chutzpah.
The cast and relevant crew members had to sign waivers that they wouldn't reveal exactly how the magic trick was done. The trick revealed on the show is slightly different from the actual trick.
The MATH in this episode included: Flock behavior, steganography and matrices - error correction code.
Colby's license plate on his black Ford is: (California) 2GEE645.
At about 10m30s, the technician was clearly not really typing, but the audio had her punching a set of keys for the .jpg file that Charlie pointed out.
At roughly the 30-31 minute mark when Colby and Megan are questioning the motel manager, one of the camera operators is briefly reflected in Colby's glasses.
Steganography doesn't work as pictured here. More likely you could have two audio or image files, between which every sample or pixel only differ a little, so the "carrier" file (into which the hidden data is encrypted) would sound or look OK. The person who has the "key" file, would then compare the key file with the encrypted file, byte by byte, to extract the encrypted data. However, this method can't hide a file with resolution equal to the carrier file resolution (one or perhaps two bits per byte only). So the image of the girl couldn't have been encrypted into the picture of the house without visibly distorting the data.
During the set-up for the assault led by Megan, an agent is holding an MP5 machine pistol with the clip loaded backwards.
[This appears on the beginning of the episode] 167 Metric Tons 5.4 Billion Dollars 1.3 Million Meth Users 2 Girls