or perhaps sue for the 4 weeks pay they now owe for leaving early?
You do not want to go down that road because you will find yourself on the dock at the end.
If people left without notice means only one thing. They weren't happy with their job.
I have handed over my notice and left on the day in two occasions over the last 20 years. (actually happened in a single year)
Might sound wrong to you, but believe me the situation was unbearable. I wasn't happy working there, the whole place was a workhouse, to the extend I put 3 stones in weight and became alcoholic affecting me over the next 4 years. FYI both those companies, had a huge turnout of employees and couldn't hold people more than 2-3 months. (software development).
So you might reflect to yourself first, and ofc you cannot bad mouth them to their next employer if they send you the reference forms to fill up.
You will be the one paying damages.