Just a couple of thoughts, and I'm not judging or being confrontational, just observations.
1 - Unless your friend is a total techno-boob, he will know that the first message was NOT part of a group text. My phone gives a different sound for group messages, and lists the numbers.
2 - You panicked, tried to cover, and involved 2 other friends in your cover-up, and decided to mislead your guy friend. In hindsight, you probably should NOT have involved others, but I can relate to the CYA aspect. Not only is it kind of unfair to them, it also INCREASES the odds of the deception being uncovered. Remember the old adage: "3 men can keep a secret....if 2 of them are dead"
3 - You went into 'stealth mode' with your guy friend, and didn't follow up on the project he wanted to talk to you about instead of calling and asking what's going on with that. Silence, on your part may give him time to put 2 and 2 together. Just as you are imagining HIS silence to mean the worst possible outcome - He KNOWS!!!!!
At this point, you are forced to play the cards YOU dealt. You have three choices: Continue the charade; come clean; or ignore it.
As George Clooney said to Quentin Tarantino in 'Dusk til Dawn': It isn't a big deal unless you make it a big deal.