The validity of a Muslim marriage can be checked through the nikahnama, which is considered integral to a religiously-valid Islamic marriage. The Qazi will maintain the nikahnama. If there is no nikahnama then the Qazi himself can testify that the marriage is valid.
The nikah can also be done though phone or the internet. It will be valid in cases where the parties make a proposal and acceptance before their witnesses and an advocate which is present.0