create a new calculated metric with the formula „if hits of [day] greater than 0 then [yournumber] else...“ (just needs a of clause for every day with different number and the original meteic i. the final “else“
The key Metric is Visit(its a key variable as well as part of the calculated metric )
Since visits are a base metric unless you made them custom somehow as in some sort of SAINT association the data gap is exactly that a gap. You cannot fill it back in. We cannot report on data not collected. SAINT uploads may have some info you can upload but I have not done so myself when it comes to uploading (manually things like visits, pageviews, unique visits).
Also see data sources. they have some limitations but may help you in part.
what happens if you slightly change your calculated formula: instead of using „equal“ try using „greater than“. then add your metricX as first parameter and the static number 0 as second parameter. and finally change the true/false values due to changed condition...