You need to ask your employer for another copy. Or you can get your W2 information from the IRS, see this….
http://www.irs.gov/taxtopics/tc159.html
Get a W2 copy from the IRS…..
https://www.irs.gov/faqs/irs-procedures/copies-transcripts/transcript-or-copy-of-form-w-2
You can get a copy of your W2 from Social Security for $126
https://faq.ssa.gov/en-us/Topic/article/KA-02501
