It depends on the insurance company, but most will accept proof in the form of a utility bill or something similar to prove where you live. I recommend calling your insurance company to find out what documentation they will require to prove your residency and reinstate your policy. Good luck and if you have any questions, don't hesitate to ask. For more information, see our additional resources below.
If you have roadside assistance on your insurance policy then it is extremely likely that your policy will cover a locksmith to unlock your vehicle. You might even be able to get your vehicle "re-keyed" under your roadside assistance coverage if you aren't able to find your keys.
In most states you are required to provide proof that your vehicle is insured before allowing you to register your vehicle. The insurance policy must meet the state's minimum coverage requirement to tag your vehicle so you will want to take your proof of coverage with you to verify your compliance with the law.