Evap tanks are prone to cracking due to stone hits. Also the area surrounding them are prone to rust from all the rubbish thrown up from the wheels. Hope you have a set of wheel arch liners on order.
Don't feel too bad. I had a mechanic do this job and they really messed it up. I think they did the same thing or perhaps worse... and pushed it up in there so it leaked...plus they missed other problems. It's sad when you pay a lot of $$$ and then basically get ripped off. (no refund from that outfit) They won the battle but lost the war. On another note: think how far you've come with this thing!