You can easily find out who their registered agent to serve papers to is by contacting your states Secretary of State. Frequently a quick internet search.
If they don't show up, you can get a default judgment against them. At which point I would take a local deputy to their store to collect. Very easy. Taking their plasma down for payment would get your point across very fast.
You seem slightly intimidated and very unfamiliar with the process. If you are going to undertake this yourself please research it. Otherwise opt for an attorney.