Unfortunately I don't know the freq used at I-69 Speedway.
I have scanned at four different tracks and here is my procedure...
All the dirt tracks I've been to in IL and IA use an itinerant frequency. First I'd scan those. Since you have a Signal Stalker capable radio, try using that feature (I've got CloseCall hits from the scoring tower/press box myself). If you are still missing the frequency(s), I'd also search between 460.700-470.000 and 151.000-160.000. Don't overlook searching between 451.000 and 460.000 (I've been to a few minor-league baseball games where simplex freqs in this range were used at the stadium).
Finding the alternate frequencies used at a track can be difficult. They are often used infrequently, mostly in the pits, so CloseCall or SignalStalker isn't likely to catch them. When I hear them say "switch to ch2", by the time I get the radio off my belt and start it searching, the conversation is always over.