The A320 has thoughtful safety features built in to the automation, eg when going into HDG whilst climbing in NAV mode, the CLB goes into open. When descending if HDG is selected the descent goes into V/S at current rate rather than open descent. Also it will not capture the glidepath unless LOC is captured first.
These guys certainly wouldn't be the first to keep on going past TOD, some even keep going past the airport. I knew someone who woke up from a short nap and was puzzled as to why the DME was counting up instead of down, he soon worked it out.