Yes a trojan can bypass netstat, usually with a little help.

In addition to the excellent advise of nihil , I would recommend a utility that has the same functionality as netstat but is external to the OS. I use Fport from foundstone. You can find it on their web site. It is free, and you can compare the results to netstat and look for anomolies.

Also is there any other device on your network where you could see the connection? Like a router or NAT device? Might look there as well if you have one.