Page 117, ArM5 says, "Wounds caused by an animal are an Arcane Connection to that animal with a life-time of a few hours". This shows that an Arcane Connection is not/was not always a part of the thing it connects to.
So, along the same lines, is a footprint an Arcane Connection to whoever/whatever made it, again with a lifetime of a few hours?
And a related question - if a magus wants to find a woman's footprints in a forest, would you consider that Intellego Corpus or Intellego Terram?
If I were to allow footprints as Arcane Connection, I'd give it but a few minutes. It's less than a wound caused by an animal. Even then I'd probably only allow it if the person was barefoot.
Finding footprints with magic would be InTe(Co), or you';d get animals footprints as well
Have a look at ArM5 p.153 InTe 25 Tracks of the Faerie Glow for tracking a specific being.
Best ask your troupe, whether - and if so, how long - its footprint is an AC to some being.
Thanks, I like these suggestions. I also like the idea that if a person is not barefoot the connection is to their boots - so you could set their boots on fire even if you can't target them directly...
Good spot! That spell addresses the tracking question as a Vision target spell, rather than the footprints/earth/individual as the target, which is an approach I had overlooked.
I'd say yes, it is an arcane connection with a duration of hours if the foot/boot-print is clear and undisturbed (as per ArM5 p.84 which states that arcane connections must be stored carefully).
That is, a clear and undisturbed footprint in soft earth is probably a short-lived arcane connection - the mere action of walking on a floor or road does not create an arcane connection.
I'd also rule that such arcane connections are easily erased by e.g. rain, meandering animals or an enthusiastic grog who discovers the track and pokes at it while pointing it out to a magus. 
Oh - and Intellego Corpus. It is an arcane connection to a person after all.
As an arcane connection I see a couple of possibilities- an animal bite leaves saliva in the wound. A footprint will likely leave some trace behind, but not something that would last long (sweat of a bare foot for example), on the other hand the foot or boot would also have picked up material that would link it to that spot- again, not for long. Finally long after (maybe even hours!) it has become useless as an arcane connection it might be usable as a sympathetic bonus for penetration as it has captured the image of what left the print.