Security lock out wait three minutes

Most of the issues with the security system on those is in the actual key switch assembly not reading the key correctly. Either because of the two wires breaking or the internal contacts that touch the chip in the key wearing out.

From the description it sounds like he moved the wiring harnesses under the dash around and you ended up with at least one of them failing. Without seeing it up close it could be as simple as taking the connectors apart, spraying them with cleaner and re-connecting. Or it could be that a wire broke inside one of them.
I would take it back and explain what is wrong. If the "mechanic" cannot get it working, take it to another shop.