Go to log of Process chain and see if it ran on 2 and 3 May. If yes, then go to the dtp and see the log. Check header tab,selections->>request id. If you see any requestid, Then go to requestid from DSO and get ODSR_* and check changelog. If there is not entry for those ODSR_*, then somebody deleted the changelog, prior to further load to cube.
Or you can see the datamart status of request loaded in DSO on 2 and 3 May, if you see the corresponding request id loaded to cube.
Regards,
Sandeep