I don't see that coolant smell resembles maple syrup, but everyone is different and that may be how you perceive it.
After any heavy maintenance, it's good to look over things carefully and search for leaks, things not properly fastened and so on. Mechanics make mistakes, that's for sure.
Check your coolant levels regularly, and in the same way (cold or hot) and make sure it remains at the same level. Remember, the level changes when it's hot. It might help to make a line and chart any loss.
As a general rule, water does evaporate from cooling systems, albeit, very slowly. It's not unusual to have to add a little water after a year or so.