Legal Question in Criminal Law in Texas

First regarding the time - that would be considered a typographical error which has no effect.

The inventory list could mean that an officer took something and didn't record it, or that they stole it. Sadly, this does happen. But, it will be your word against the officers'. And, even if they concede that there was something taken that was not listed on the return, this would be an error that has nothing to do with the search or finding of illegal substances.

With regard to taking the xanex tabs - while searching pursuant to a warrant for the marijuana, the police were allowed to take anything that on its face was illegal. If the pills were in a bottle with your son's name - his prescription - then they could not take them. If they were just lying about, then they could take them. (This case could be dismissed if your son is able to produce a prescription for the tabs.) To give you an example, if the officers found an illegal weapon - say an Uzi or a sawed off shotgun - they could have seized those, too, because they are clearly illegal even though they are not marijuana or even drugs.

Your son needs a good local lawyer to represent him. While you have not stated any grounds for a motion to suppress illegally seized evidence, there may be grounds somewhere - and oftentimes it is in the affidavit that was used to obtain the search warrant. A lawyer will be able to review this evidence and determine if there are suppression issues.