There are always signs. Either in the language he uses, how engaged or distracted he is when he's conversing with you, body language, etc. Look deeper for those clues. I can guarantee you when you find somebody that's truly into you - it's going to look and feel a whole lot different than this guy. So keep looking for clues and signs.
every situation had clues and signs of what was about to happen.. EVERY situation.
If you ca't find it it's okay. no big deal. but they are always out there so its in your best interest to learn and find them as much as possible so it doesn't happen to you again. The less you learn and figure it out, the more it'll keep happening. and we don't want that (I DON'T want that) to happen to you.
CLUE: the "i'm busy" with no explanation and making excuses - that's 2 of the clues!