Des Raj Kapur died in October 2013 after he was found severely dehydrated and barely conscious at the Burroughs Care Home in Hillingdon.
A representative told West London Coroners Court it could not find records of any fluid and food given.
His son Deepak Kapur said he was "angry" at his father's treatment.
Mr Kapur said his father had been a "lovely man" who just cared about "tending to his family and his family's needs".
"There have been shocking failures in his care."
Prior to being admitted to the care home for the second time, Mr Kapur had become immobile and needed help washing, feeding and drinking, his son said.
Mr Kapur said: "They were supposed to look after him and tend to all his needs".
The coroner gave a narrative verdict which said a lack of fluid intake contributed to Mr Kapur's death in addition to the five illnesses he suffered from.
Care UK said it "apologised wholeheartedly".
A lack of fluid intake contributed to the death of an 85-year-old man at a home he went to for two weeks' respite care, an inquest has found.