Originally Posted by jiejie

OP doesn't have a visa, he's clearly doing TWOV despite his original post that mentions "144 hour transit visa" which we know there's no such thing.

My counsel, though it may come too late, would be to go to the Immigration Office/PSB on the public side of the airport, show your original plans and tell them you are ill and need to change plans so you go directly back home to USA instead of to HKG. Ask for a release from the regular TWOV requirements and a note from them allowing an exception. I'll bet odds are better than 50/50 they will grant this and notate the database/your TWOV stamp to allow this to happen and let you get through Exit Immigration unscathed.