Funny though how everyone assumes Locke is lying just because he is a sneaky fellow. There really is no proof that the guard is honest. Maybe he did rip Locke off, you can't be a 100% sure.
Are you saying that mindreading isn't 100% foolproof and can't be tricked? Now that's interesting. It is hard for me to imagine that some soldier who, probably, never heard of mindread and has no special powers/abilities, can resist mindread. But oh well...
Your point being? He can't resist mindread and there's nothing in his mindread that reveals more about his relation with Locke, only Richard.
It's obviously implied that Locke is playing tricks, but you can't be really sure.