How do I report a lose from a theift

Sorry--casualty losses and thefts are not deductible under the new tax law.  Only casualty losses in federal disaster areas can be deducted.

https://ttlc.intuit.com/questions/4482394-how-will-tax-reform-affect-my-2018-federal-tax-return

In case it helps, some states do not conform to the new federal rules xmasbaby0 mentions so for state purposes such non-qualifying losses can still be entered as "This event does not qualify as a disaster casualty". This loss will be ignored by the federal program unless there is also a casualty gain in the return whereupon the non-FEMA loss will offset the gain.
A nonconforming TT/State program will pick up the loss.

My list of the nonconforming states is AL, AR, CA, HI, IA, MN, MO, and NY. So if you are going to prepare one of those state returns then it could benefit you to enter it into the federal program.