‘In the presence of’ is subtly different from simply being enclosed by the same location as, since it also takes account of concealment (see WI 7.12 and Example 99: Today Tomorrow). So to fully replicate it, perhaps:
if a person is enclosed by the location of the scalpel and the scalpel is not concealed:
being touchable by a person is a subtly different concept again…
EDIT after a little experimentation, it’s more particularly the case that to be ‘in the presence of’ something, that something must be in scope for the actor (but not necessarily visible or touchable or not concealed):
for example, in the above scenario if you make the scalpel concealed, or the room dark, or enter a cupboard and close the door, you’re no longer ‘in the presence of’ the scalpel, but if you add a rule to place the scalpel in scope, you’re back in its presence in all these scenarios even though it remains concealed and/or not visible and/or not touchable.
So in a nutshell, ‘in the presence of …’ means ‘when the … is in scope’, and the reason an actor is not ‘in the presence of’ a concealed object is simply because such an object is not ordinarily in scope.
EDIT 2 This is confirmed by the I6 generated by ‘in the presence of’, which calls the I6 routine TestScope(object, actor).
The fact that ‘in the presence of’ is defined by scope explains why in I7 it only exists in the context of actions, which is the only meaningful context for scope. There is no other straightforward way to test for scope in I7 (the I6 routine TestScope(object, actor) could be used if necessary).
For more details on scope in I7, see here.