Yes this is possible using two calculated fields for your measure where you set the result to zero if there is only one record showing and sum([measure]) otherwise for your line, and the opposite logic for your bar. Add both calculated measures to your view and set them as dual axis (and sync the axes). See an example attached.
I would question why you would want this though -- it's still going to look ugly... If you are using this in a dashboard, have you considered changing the filter to a highlight instead so your datapoint stands out, but still shows it in proportion to all the others?
More info about dynamically changing marks here:
mark type change.twbx.zip 14.6 KB