R.I.P. Scout26
Another option is they make lockable covers that you can put over your outside water valves. https://www.grainger.com/product/ABILITY-ONE-Gate-Valve-Lockout-52ND74?breadcrumbCatId=5537&functionCode=P2IDP2PCPhttps://www.grainger.com/product/ACCUFORM-Gate-Valve-Lockout-10K122?breadcrumbCatId=5537&functionCode=P2IDP2PCPThese links are for safety lockouts on larger gate valves, but they probably sell something for garden hose valves also. I never looked for them at Lowes. Might be worth a few dollars to make it more difficult if you think theft is the cause.