"Uh... I guess you didn't read the part about it taking ten miles before someone from behind came up, ..."
Exactly, that was ten miles where in the end, the pace for you and the paceline was the pace of the group without you, and with you doing more work than each of the riders in the paceline since you and the group covered the distance in the same time, but with you never drafting. Had you waited, you could have added your strength to the existing group's and the result would have been the group with you in it would have been faster than you alone plus the group alone. I can say this because you were strong enough to hold the group off for at least ten miles. As to no one being in sight behind you, how is that possible? You said the course had a turnaround, so you should have seen what was coming up there. Even if you didn't, the group you ended up with must have been in view for some time before they caught you. From your description, it doesn't sound like you ever saw them and waited.
Exactly, that was ten miles where in the end, the pace for you and the paceline was the pace of the group without you, and with you doing more work than each of the riders in the paceline since you and the group covered the distance in the same time, but with you never drafting. Had you waited, you could have added your strength to the existing group's and the result would have been the group with you in it would have been faster than you alone plus the group alone. I can say this because you were strong enough to hold the group off for at least ten miles. As to no one being in sight behind you, how is that possible? You said the course had a turnaround, so you should have seen what was coming up there. Even if you didn't, the group you ended up with must have been in view for some time before they caught you. From your description, it doesn't sound like you ever saw them and waited.