I-Did-A-Run 10K 2004

I went to the I-Did-A-Run race this morning thinking I would run the 5K. I had registered a few weeks ago, and when I got my bib, it said I was running the 10K. I forgot what I signed up for.
I didn't expect much because I was as sore from last Sunday's Grand Canyon crossing as I would have been from a marathon. But I felt fine warming up, and when the race started I cruised pretty easily at a good pace through the first mile. Here are my splits, but you can see that the course measurement was all messed up.
The 10K was just once more over the same loop as the 5K.

mile time split
1    6:37
2   13:42 7:05
3   19:24 5:42
3.1 20:06
4   26:43 7:19
5   33:39 6:56
6   39:29 5:51
6.2 40:49 1:20

The third mile (also the sixth) had to be short. The whole course had to be short. I was thrilled to run close to 43 minutes in February. Most of my recent 5K times have been around 21 minutes. There's no way I ran a 10K in that time on a dirt trail a week after crossing the Grand Canyon.
A volunteer near the finish said that the course was 2 tenths of a mile short.
That would still put my time between 42 and 43 minutes.
I got third in my age group. I finished with a good kick. I know I could run faster if I was more rested.
I feel pretty good about this, but I have to wait to see if I can do well in another race, because I'm so uncertain about this one.