How to fix a toilet that no longer swooshes when it is finished flushing?
Definitely, snake the toilet to confirm he didn't flush something bad or leave his rag in that was used to plug sewer gases out until his work was done. Some guys shove their rag in &amp; out of sight to then forget about it.

Depending on the setup the shower could have cleared the rag from the shower &amp; right into the toilet elbow. If you do hit something mushy with the toilet snake immediately or in a couple or few feet, then it's likely his rag. If it's not in the toilet itself, then the toilet has to be removed in order to retrieve it...So it doesn't get caught somewhere else where it can't be removed easily.

If you aren't comfortable with that &amp;/or don't have a new toilet seal on hand, then absolutely get him back ASAP to fix whatever he did.