With a C.I. and a detectives testimony of a transaction taking place in an alley behind a business (a supposed drug hand off)a search warrant was issued. Now if the transaction that was seen was a friend of mine handing me a sobe drink (found at any liquor store)and a hand shake saying"thanks 4 the drink". Wouldn't this search warrant that was issued be contestible even though they found drugs during the raid? They did not stop the vehicle that day even though they supposedly just saw a drug deal occur. I can have that person testify and that person has no criminal or drug history.

You can't prove it was a sobe
Your friends testimony would be taken as 'sticking up for you'
Any more they use any excuse they want to search.

No, first they don't need both a CI and the officer to get a search warrant, a CI is all they need, to tell the officer, the judge will want to know if that CI has provided good evidence prior to the officer, if not, the judge may or may not issue it, sometimes depending upon the officers tract record of having good CI. Also it will depend on what was actually seen, In general the CI will have had to see drugs perhaps in the place, and then the officer sees what appeared to be done. The simple fact is normally unless it is bought into question in pretrial motions, you will not know what was on the application for a warrant.

But since drugs were found, the court will assume it was drugs since there is no real proof to show it was not.