The only thing that freaks me out about substitution is getting it into the bathroom with me. I have never been drug tested before and some people tell me they are patted down before using the bathroom
Then why would you consider sneaking in an additive if you fear of being patted down?

Nevermind answering that question. The truth is, the clinic personnel will not pat you down. Thats the job of a police officer. And since youre merely taking a drug test for a job, and youre not a criminal being placed under arrest, clinic workers cannot frisk or otherwise touch you in any manner. This constitutes groping and is against the law.

Substituting a sample for a random test can be had. You could always delay the operation by stating that you need to go home and get your picture ID. By law, a picture ID is required for all specimen collections at the clinic. No exceptions. This also applies if a mobile collection unit (van) appears on the job. Going home to "get the ID" will buy you enough time to heat up the sub sample.