Thinking man,
You asked me on page 1 what i meant by "losing a company 401k", but I think that has been thoroughly answered on page two of your thread here.
The last retail company I worked for went bankrupt, and all 401k participants had to file as creditors to the company to even think of getting any money back. It seems the company, who had a 401k program invested in its own stock, then failed to pay the administrator, and somehow had raided the plan for "operating capital" to keep the doors open. It failed still. People who had money tied up in the 401k, even at 100% vested only received about 1% of their funds, and fees to transfer funds directly was taken out of that. I read all this rather than experienced it as to my way of thinking, a 401k mostly or all invested solely in its own stock is a bad idea to me. But I got all the paperwork involved in the 401k debacle as a former employee and potential 401k holder. .
I think the few examples given plus my "warning" if you will, should give you pause.
You may have a successful 401k left at another company, but not all 401ks are equal.
Faced with a company in jeopardy, even if they only appear to be doing "seasonal layoffs/rehires" I'd not want to keep my money with them, I'd rather keep it under my control and in my hands.
But your ideas may be different, I just would not be surprised if it fell through. Let's say you don't work for then for the next 25 years and they appear to be doing well. But since you aren't involved you may not see their journey towards insolvency. And then wham! You find out your stash with them is going going gone.