If McLaughlin could play at lock, Leinster wouldn't have needed Thorn. The only people who seem to think that he was a possibility in the second-row are the ones who thought he should have went to the WC ahead of Ryan/Tuohy/McCarthy.
Selecting McLaughlin for the second test was an odd decision as both POM and Henry had better seasons than him. Admittedly, he did do well in that test. The less that's said about his "performance" in the third test the better.
In fact you could say it about basically any player on the pitch. Everyone was rubbish. Why McLaughlin needs to be singled out is beyond me. Especially considering he put in by far the best performance of the tour between himself, POM and Henry.