Do you have cluster configured on this Application?
If yes then let me know configuration details.
If not , then how many contents are there of type that you are looking for?
As for optimization point of view lucene has limited search result size upto 1000 only(By Default), it is possible that you because of this limit lucene is not searching document which you are looking for.
You can increases the search limit into alfresco-gloable.properties file , by changing value of this properties index.tracking.maxRecordSetSize=1000
Best Regards,
Hetal Patel,
CIGNEX Tech.