How can I rebuild my missing logbook after 20 years of not flying?
You will probably not be able to recover any solo flight time you have completed to this point, but contact your previous flight instructors in Illinois.  They should have logged the training time they did with you on dual instruction, which will allow you to recover that flying time this way.

If you don’t have contact information on this instructor, you may be able to search them out, either on the FAA’s website or third party flight instructor directories like this one.

http://www.iflightplanner.com/FlightInstructors/

Good luck