Are you really sure that it was fuel ?
The RR Trent like all (most) other engines scavenges and vents overboard all of the 'slop' accumulated whilst on the ground - Water, melted Ice / Snow, overfilled Oil, overfilled Hydraulic fluid, and yes, even some fuel.
And YES, you did do the right thing in reporting it. Most times it is a false alarm, but sometimes very real.
Regards,
Old Smokey