You should have continued to get statements from the plan that is running the account. You should contact each of your former employers and ask that they give you the information regarding your 401K and make sure they have your current address.

Unless you have moved and did not notify the old plan administrator or your old jobs HR department you should have been getting statements of some kind. Also, it costs your old employer money to keep you on their 401K plan so many companies opt to cash you out and from there you have the option of rolling over your 401K into another retirement account or just keeping the money. You note that you had several different jobs where you had 401K's. Your employer, in each case, should have given you your options regarding your 401K at the time you terminated employment with them. Are you saying that none of them did that?

So, call your old employers and ask what happened. They would know who you should contact or they themselves should be able to give you the information you need.