Losing your green card might be alarming, but it doesn't have to be a crisis. It's fairly easy to file for a replacement of a Permanent Resident Card -- for a hefty fee. The United States Citizenship and Immigration Service usually cooperates if there's no issue with your residency status. Withdrawing the request is also a possibility, as long as you follow procedure, but getting a refund for the application fee won't be in the cards.
Purpose of Form I-90
The formal name of USCIS Form I-90 is Application to Replace Permanent Resident Card. You use this form to replace a lost or stolen green card. You can also use it in case the original green card was mailed at least 30 days prior and was either lost or stolen in transit to your home. Finally, if there is any incorrect information on the card, the I-90 is the application to file to get a corrected version. You can withdraw the I-90 after you've submitted it.
Documents and More
You must submit a copy of the original Notice of Action, form I-797. This is proof that the agency approved your application to either establish your permanent resident status or adjust your status from a non-immigrant classification. If the card has errors due to clerical error, you submit a copy of Form I-551.
Fees and Exceptions
The fee for an I-90 application, as of December 2013, is $450, which includes an $85 charge for biometrics (i.e. fingerprints and other personal data). There is no fee if the USCIS issued the card but you never received it, or if due to a clerical error on the agency's part, the card has incorrect information.
Withdrawing the I-90
When you submit an I-90 application, you will receive a receipt number from the USCIS that begins with either LIN or MSC. If you wish to later withdraw the application (if, for example, you find the card or have it returned), you must send a written request to either the Nebraska Service Center (for LIN receipts) or the National Benefits Center in Lee's Summit, Missouri (for MSC receipts). The USCIS does not refund application fees.