Saved search missing results

I'm using getRange() to get the results of saved searches.

It appears for certain ranges of numbers the search erroneously returns zero results. There is no error message thrown that I can see. The broken range returns more quickly than the searches that contain results.

I ran searches w/ different ranges and output the count (number of rows returned) for each start/end range:

{start: 0, end: 1000, count: 1000} // results w/ count of 1000 look OK
{start: 1000, end: 2000, count: 1000}
{start: 2000, end: 3000, count: 1000}
{start: 3000, end: 4000, count: 1000}
{start: 4000, end: 5000, count: 1000}
{start: 5000, end: 6000, count: 1000}
{start: 6000, end: 7000, count: 1000}
{start: 7000, end: 8000, count: 1000}
{start: 8000, end: 9000, count: 1000}
{start: 9000, end: 10000, count: 0} // Why is this count zero?