This is not intended to be legal advise or as legal representation. I am a California personal injury attorney . Be aware that every state has its own statute of limitations; and statutes & case laws that govern the handling of these matters.
There are no requirements that CBP stamp the passport of a US Citizen upon return to the US.
The practice began so that Customs or I&NS (now CBP) could obtain information on your travels. All of the information is now available through the Advance Passenger Information System
This should not be construed as advice, only information and I recommend for any additional questions you seek the advice of experienced immigration legal counsel. The posting of a response in no way infers client - attorney relationship has been established.
i added an immigration tag to your question. I am not an immigration attorney, but do a lot of international travel. Anytime you come into the US through customs, your passport is electronically scanned, so you should not have any problems.