I solved my problem by specifying the getField function to look at the header. So:
sendingTime= quickfix.SendingTime()
print sendingTime, "\n"
message.getHeader().getField(sendingTime)
print sendingTime, "\n"
The first printed line will be the sending time with milliseconds rounded off (I have no idea why), it lookes like 52=20130207-02:38:32
The second printed line actually looks into the header (where field 52 resides) and gets the whole field, it will look like:
52=20130207-02:38:32.212
This explains why when I tried message.getField(sendingTime)
I was getting a Field not Found error.