Want to offer something... Don't see any reason to jump to conclusions that the person driving that truck is a "snatcher." It could just as easily go down like this...
A. Driver is coming west on 10th street and trying to get a jump on the day for lawn work, landscaping, construction or mowing. They are taking 10th as they cut across town from the east side. Remember... that period of time was WAY hot here with forecasts putting the temps in 90's which would explain someone being out just before dawn.
B. At the corner of 10th and College they glance over for oncoming traffic and see "something." That might be a staggering, 4 foot, barefoot blonde or that might be an argument or anything out of place.
C. They go ahead and cross College and then stop at Morton. They decide to take a turn and circle around for another look.
D. It's possible they pause at the intersection of 11th and College to watch or drive around again but they do so at a different intersection. We don't know because we don't know what LE knows and what LE might also have on camera. Remember, LE did say that the time stamps may not be dead accurate.
E. They then make a final lap and either don't see her anymore or decide to get on with their day. They turn on 10th. Decide to blow through the intersection of 10th and Morton and go on with their day.
Regardless, it's very probable they might have seen something incredibly important and LE is right to want to find them. The problem with this theory is how do they NOT know what's going on and somehow feel like it's not important to come forward and say what they saw.