There were a couple of things AM said that made me wonder if he was mis-remembering (it happens, especially in a highly stressful time like discovering your sister is missing) or if BM actually just lied to him.
The landscape job in CS, instead of Denver, and the 6pm v. the 9pm arrival, and then TN showing up. There's no question BM is actually a liar, since we have him telling TD he's been cleared (lie) and telling family he passed a polygraph (lie), so it's hard to decipher if these are more lies, or if AM got things mixed up.