its pretty much a given that your insulation will be compressed and moved about. the time to have done this..
if indeed it can be done..was prior to insulation install.
maybe from the other side of party wall??

if the missing row of brick is above your insulation
whats the problem? it is only if air is moving thru the insulation that it derates it.
as your thermal boundry is the insulation on the attic
floor missing brick above this shouldn't be an issue.

best of luck.

Just make sure whomever does the repair uses the correct mortar.

Lime mortar is not generally available and must be mixed from scratch.

If you use type S (the common grade in the big box stores) it is likely to cause further damage to the old soft bricks.