This is due to the fact that you rely on sketchy and not agreed upon information in your search.
None of the scholars of Hadith added this numeration it was added much later in our modern days due to the fact that these addition may help referring to a hadith within a specific edition of a book. While this information would not be helpful in any other edition. So without the information about the edition it refers to the number is useless.
Note that it is said that imam an-Nawawi re-arranged Sahih Muslim and gave each section titles so the arrangement we accept today is mainly made by imam an-Nawawi when he started commenting on the book of imam Muslim. And I'm pretty sure that if early hadith commentators would have referred to ahadith within Sahih al-Bukhari or Sahih Muslim etc. by numbers their references for the same hadith would differ a lot. Especially as many of these sources were work in progress and some of them were not finished by the author himself, but by a student or scholar who came later and intended to finish this great work, so the original author may not necessarily followed a (known) order while working.
For example the amount of ahadith in al-Muwatta' vary from around 700+ to 500+ depending on the narration. The total amount of narratives and statements in that book vary between around 3000 and 2200.
For other works different scholarly counts may leed to a smaller deviation.
For example in Sahih al-Bukhari, ibn Salah and an-Nawawi claimed that the amount of ahadith including repetitions is 7275, while ibn Hajar counted 7397, however it depend on how to count: if one counts the introduction ahadith of each chapter too or only the musnad ahadith or only one instance of a hadith or each different chain of a hadith makes a difference which could lead to huge deviations.
When you search it is always best to search by keyword. By the sahabi on whos authority the hadith was narrated or by topic the more information you have at hand the easier and better your result will be.
And the most helpful information would be to have the Arabic original wording of the hadith quote at hand.