You can either apply for citizenship or file an application for a current green card. You should consult about the matter with an immigration attorney if you have had any arrests or convictions in the past.
You can apply for the new card by filing an I-90 with the USCIS. You have not lost your status as that has to be formally taken away by the government or you have to renounce it at a US consulate abroad.
Myron R. Morales, Attorney
Not being able to prove that you are a legal permanent resident.
J Charles Ferrari Eng & Nishimura 213.622.2255 The statement above is general in nature and does not constitute legal advice, as not all the facts are known. You should retain an attorney to review all the facts specific to your case in order to receive advise specific to your case. The statement above does not create an attorney/client relationship. Answers on Avvo can only be general ones, as specific answers would require knowledge of all the facts. As such, they may or may not apply to the question.