There is absolutely no rational reason for continuing to use the "Toilet Flush" as an excuse for these raids.,p> The drugs or anything else are destined to be located in either the public sewer or in a private septic tank.
In the instance of the private facility, you can dig it up at your leisure. In a public sewer, all one has to do is open the cover on the nearest downhill manhole and throw several sandbags into it to prevert the flow of effluent in the line. Again, one can recover the goods in a leisurely manner.
Decades ago and in something of a previous career I got to witness several drug raids on mobile homes. The rookie on the raid was always assigned the job of getting to the sewer connection (mobile home so would be just an easily accessible plastic pipe) pulling it apart and catching whatever came out as the raid started. Today someone would probably be given full HAZMAT gear for the job.