Lets address the important question first:
Is this something I should be concerned about happening to me in the
If a company is going to lay you off they are not going to let you return to work. There is too much risk in it for them not the least being your making the poor decision to damage the company through your internal actions. For this reason when a company lays you off they remove your access to the location and are not going to allow you to continue working.
When you are laid off(or any permanent termination type) there is a lot of paperwork that the company needs to fill out to comply with the law. If they do not fill it out then you are not terminated. If they stop paying you anyway then you can sue them and not only get back pay but damages that result from their failure to pay you. For that reason it is incredibly unlikely that it will happen at a company that is solvent. It does happen at companies that are on the brink of going under but that is a different question.
If the company did all that paperwork and still let you continue to work then it would still owe you for that time that you worked. Of course if you do this in hiding and during off hours they can fight it but if you were in a position like Milton where you work everyday like normal and the company just lets you continue then they have agreed to keep you on. They would need to do all new paperwork to terminate you if they allow you to work. So, No you do not need to worry about this happening to you.
If it happens to you anyway then you would need to get a lawyer, preferably one that is knowledgeable in employment law. Lawyers that handle workmen's compensation claims usually will handle these cases as well or at least be able to refer you to someone who can help you.