So the last mechanic to work on the car (MK2 3.8 MOD) forgot to tighten the oil filter 
and I lost a bunch of oil as a result.
It was full to the top of the mark on the dipstick when I first got it back from the mechanic and needed 2L of oil to top it up today after noticing the issue.
How likely is it the engine is damaged as a result?
Not particularly likely, especially if you did not lose oil pressure.
Mr Wiggles that is the best news I have had all week! thanks 
badly needed some good news, it’s been one of those weeks and it’s only Tues afternoon
Welcome! I had a customer who loved changing his own oil on his E Type: After he left, I got a call from him about 5 minutes later, asking, “Could you come to XXXXXX, bring a wrench and a few quarts of oil?”
I was able to follow the trail of oil, directly to his location. He’d forgotten to put the o-ring under the filter canister…!
oops, easily done though.
can’t wait to move to a new house with room for a pneumatic lift in the garage so I can take care of a lot of the work myself, if you want something done right…
No worries with an oil lost of that magnitude. Ive had customers run their 3.8s two quarts low to minimize the oil leaks. LOL
oh god - that’s scary!
if it leaks it means I has oil 
Or rather, if it doesn’t leak, it’s out of oil!
one day, I will have it leak free (maybe). although i suspect it doesn’t actually leak oil but attracts it from the surrounding environment and collects it under the engine
Date: 25 Oct 1993 12:49:32 U
From: ‘‘Rob Reilly’’ [reilly@admail.fnal.gov]
To: ‘‘Jag Lovers’’ [jag-lovers@psy.uwa.edu.au]
Jaguars do not leak. The Jaguar engine is actually an oil
magnet. The oil in the primordial soup deep within the earth
coalesces into a pool at ground level below a Jag engine,
with each tiny molecule straining to defy gravity and leap
up to the oil pan, where they know their brothers are living
in eternal bliss. Some of them are able to make the leap,
and they then form gangs on the suspension cross member,
plotting how they can get past the pan gasket guards. Two of
their revered heroes are those intrepid Irishmen the O’Line
brothers, Hav and Valv, who led an assault on an E-Type,
only to be repulsed by a cowboy named Perma Tex.
I kid you not.
that is brilliant Rob!
I think I am going to have that made into a sign to hang in the garage