The first few hours after a theft are absolutely critical to getting the word out & preventing resale of the stolen gear. If your gear is already registered, then you just have to sign in & flag the items as stolen (and optionally provide additional information).

If you wait until after your gear is stolen, you'll have to add the gear, verify it with something else other than a picture of the serial number and wait a day or two for someone at Lenstag to approve the verification request. By then the gear has probably been pawned or sold and the chances of successful recovery are substantially lower.