If you were laid off, you must learn about the WARN Act
Search for postings on this site or search for articles as follows: "WARN ACT" and Illinois (or whatever your state)
The WARN Act is a Federal law that indicates that, under certain circumstances, the employer must give you 60 days written notice before a layoff (and pay you for those 60 days, in addition to any severance). In some cases, employers don't comply with the WARN act.
In other cases, the employer sequences the layoff to avoid complying with the WARN act.
Since the WARN Act is enforced by the Federal Department of Labor, search WARN and DOL.
Most states also have a WARN act, and that is why you should also check with your state agency that enforces the WARN ACT. If your employer failed to report layoff metrics to the state office, the state office will order the employer to do so
Hang in there.