LF: Kidnapped!Don and Amita

[jestana]

I remember reading this fic where Don and Amita are kidnapped because the kidnappers think Don is Charlie. In order to buy themselves time, Don writes random math stuff on the chalkboard provided. After he and Amita escape/are rescued, Charlie looks at what Don wrote and says that it actually has potential as an equation or something.

Any help would be appreciated.

Edit: Found! Simulacrum by valeriev84

Oh, and it was Megan who was kidnapped along with Don, not Amita. *sheepish* Though the bad guys thought she was Amita, so maybe that's why I was confused.