back into another trailer and scraped the side of it

by Keith
(Texas)

was in California and was backing into a space at a truck stop. scraped another trailer, no ticket issued because it was in a private parking lot. the other driver and I exchanged info. they (other driver) called my employer's insurance and they said that my employer didn't have insurance on the trailer ( to my surprise ) now the insurance company for the other company is coming after me for cost to fix there trailer and down time. my question is, I thought that if trailer is hooked to tractor it would be insured. the company I work for is out of Texas. does Texas require the trailer to be insured. thank you in advance for any help in this matter. there insurance company wants me to pay almost five thousand dollars, money I don't have.