If not using Service Portal, create an onSubmit Catalog Client Script which passes the Short description variable value to a Script Include via Glide Ajax.  The SI will query the hardware model table for a value matching the short_description field and the variable value passed in from the client.  Back in the client script, return false and show an alert/message if you want to prevent the submit.  If using Service Portal, a common workaround is to do the same onChange of a mandatory variable, clearing that variable if the record is found to effectively prevent submit.