Answers
You are not alone, every year, millions of Americans leave 401k's at former employers. The good news is that the money stays yours...no matter how long you have forgotten about it.
The best way to track down an old 401k is to call the 401k provider (e.g., Fidelity, TransAmerica, Schwab, etc.). If you can't remember the company, then try calling your former company to ask about the provider at that time...sometimes this can be tricky if there have been several mergers. Or, you could try finding old tax returns that may contain this information.
There are a few online resources that help people track down old accounts:
https://www.askebsa.dol.gov/AbandonedPlanSearch/
https://www.unclaimedretirementbenefits.com/
Good luck!
**All above answers are provided as general information only. No warranty is made regarding the fitness or accuracy of the information provided in this answer. You should seek advice from a licensed CPA, attorney or CERTIFIED FINANCIAL PLANNER™ as to your unique financial situation.