missing a shot before going back to subs

[black2reality]

So a friend of mine has been going back and forth between taking subutex (around 4-6mg daily) and using (smoking .4-.8 ). (He knows that this is not advised but that is not the question so please save your breath, he has been really trying to do the right thing for himself, and at the end of the day thats what he is trying to do now). Most recently he did: about 5 days on subs -> 36 hours using -> 36 hours completely clean -> about 5 days using (the first couple days using moderately and taking 8-12 breaks in between, but the last couple days he used relatively heavily and consistently). At the end of his bender he had two points left, he finished his stash in the morning by IV'ing one pt and smoking one. Unfortunately, while he says he registered and double checked, he missed at least some of this last shot because he said the rush was not as strong and his inner elbow (injection site) was a little red, swollen, and sore. It is better now (a couple hours later), but he says he is still a little sore and it is still visibly noticeable.

Now the questions. He always waits 24 hours after his last dose before taking his first piece (2mg) of subutex so as to avoid precipitated withdrawals. - but this time there are a couple of factors that he is concerned about. Could you please help him out by answering the questions below and adding any input or other info that he might find helpful??

1. Does dope leave your system faster or slower when IV'd (vs smoking)? or is it the same?
2. If the user misses some of his shot, meaning that it is slowly getting absorbed into his system, would he need to wait longer to take his first dose of sub (so as to avoid precipitated withdrawals) or will this not make a difference?

Thanks for your help in keeping my buddy healthy and keeping me from getting a headache