Three hours will not recharge a battery, looking at more like 8 hours, and if it was that flat for any time then a lot more, batteries will only accept so much power when charging, using a smart charger is best as it tells you when finished, I use a cheap Lidi charger, it has four bars when all are lit then charge is nearly complete, I will wait for voltage to be over 13 volt before removing charger, as even after it goes to final stage, it is still charging the battery a little.
Years ago we would put batteries on an equalising charge once every two months for 24 hours, however both the cars charging system and the batteries have improved since then. Today my wife's Jaguar XE auto disconnects items should the battery fall below a set level to ensure the battery does not discharge enough to stop charging, don't fully understand why it failed to start with us, the agents said faulty battery, but changed rear battery and I thought front one was for starting, so even with all the computer control still had problems starting.
However again putting the battery on charge can also upset the on board computer it seems, it monitors the volt drop to work out battery condition, however if you use a smart charger their output is so low they are unlikely to permanent damage anything, so I would aim to charge for at least 24 hours if not whole week.
Not sure what level of control the 2008 Ford Fusion has, Jaguar was owned by Ford for a time so Ford may have same system, however back in 2008 there was so much less in the car, so likely a boot not closed fully could cause boot light to stay on, and in my old car you can leave interior lights on, and at 12W = 1A then with a 60 Ah battery after 60 hours battery completely discharged.
When my father-in-law let his battery go flat, could not open bonnet as slightly under work bench in garage, could not release hand brake it was electric, so it was trolley jack under back axle and drag it out of garage with my car before we could even lift bonnet to charge battery, lucky not a 4 wheel drive car. At least with car parked outside I can see if a lights left on in my car, unlike my wife's XE I can't check car with smart phone, I have to go outside and switch on ignition to see how much fuel is left, or to warm up engine before driving off. But her phone did not help her start engine when battery was flat! Sorry should say discharged, shape of battery does not change be it charged or discharged.
But 3 hours is not enough to recharge a lead acid battery, most need at least 8 hours, the VRLA as used in Jag may be a little faster, they are also more expensive over £200 and seems we were not charged for labour?