where is the missing versions

[Gu Shiyuan]

Hi,
   svn log gives me a list of the history, but I notice that some versions
are skipped. In the list, r44 is followed by r49 while r45-r48 is missing.
How can I find out those versions? I remember I made some important comments
when I commited those versions, but I don't not why they are gone. Thanks.