Former Illinois State Toll Highway Authority employee checking in here… First, don’t bother contacting IDOT, they aren’t related to the Tollway, except that both are in Illinois and manage roads. It looks like you’ve already tried the online route, which is here. Since you couldn’t pay that way, you might want to call the Tollway at (630) 241-6800, and ask for violations. They should be able to get you paid up pretty quickly.
To address some other items listed in various postings (note that the comments below are not aimed at any posters, just general clarifications): The Illinois Tollway sends out its own bills, so it should be coming from there and not some other entity. Violations are (I believe, but don’t quote me): $20 + toll for first billing, $75 + toll if you don’t pay after a certain number of days.
It is absolutely illegal to run a toll even once, you don’t have to run it 5 times before it becomes illegal. (Maybe I should open a GD about why people think it is okay to steal from the Toll Authority but not from the grocery store…) If you DO run one 5 times, expect to see a bill for $100 + the cost of tolls. This bill will escalate to a much higher amount if you ignore it. ISTM that it would be much easier to either pay the toll when you go through, pay using the missed toll system, or even pay the first violation at $20 rather than $100 for 5 or $200 for 10, etc. However, the Tollway had some offenders with huge bills (over $10,000) when I was working there, so something might be flawed with my reasoning. Keep in mind that if you don’t pay the Tollway can also suspend your license and/or your tags (not sure if they can do this in Canada, but they were definately able to in Illinois and several other states).
Problems with the toll booths do happen. Each plaza has several cameras and a couple of methods to detect cars. Usually on IL’s system the computer will detect a problem, shut down the lane, and remove missed toll notices automatically. However, as with all systems, I’m sure that some slip by. While license plates are OCRed, violations are also manually inspected to ensure the computer caught the plate correctly.
Toll collectors on the Illinois Tollway should be relieved by another toll collector or manager if they need to use the restroom. There are quite a few unmanned plazas with only coin baskets, but they are clearly marked as such everywhere I’ve ever seen them, and are also detailed on the freely available map.
If you let me know exactly what signage was confusing, I will try to pass that along to someone inside. They have done a lot of research and work to make the signs as clear as possible.