A court has now rejected her legal bid, saying that she had no legal right to demand the data from the hotel and did not provide enough information to be sure of the man's identity.
The court argued it could also breach the privacy of four men named "Michael" who were registered at the hotel at the time.
The judgment was reached last October but was only recently made public.
According to the court, the father's right to self-determination of his own information took precedence over the woman's right to child support.
Publishing its decision under the title 'Father Roulette', the court wrote: "This right is affected by the exposure of the data because as a result, the possibility of [the man having] a sexual relationship with the complainant, as the mother of the child, would be irrefutably placed in the room."
- Originally published in Telegraph UK