Cristian Montano made his senior debut as Notts County were beaten on penalties by local rivals Nottingham Forest in the Carling Cup first round.
The 19-year-old forward, who joined the Magpies on an initial month-long loan last Friday, appeared as a 63rd-minute substitute in front of a 21,605-strong crowd at the City Ground - more than 6,000 of whom were supporting Montano and his team-mates.
Montano, who has been in fine form for the Hammers in pre-season and travelled with the first-team squad to Switzerland, joined the action with Martin Allen's side trailling 2-1 to their neighbours.
Fellow substitute Graham Westcarr equalised with a low shot with 14 minutes of normal time remaining and, after coming close to winning the tie in normal time from Montano's cross, striker Lee Hughes put the League One side ahead eight minutes into extra time.
Wes Morgan scored a last-gasp equaliser before misses from Hughes, Hamza Bencherif and Neal Bishop saw Forest edge through 4-3 on penalties.
Earlier, Mike Edwards had put County ahead before Lewis McGugan and United States international striker Robbie Findley put Forest 2-1 up eleven minutes into the second half.
Montano will hope to make his League One debut at home to Chris Powell's Charlton Athletic on Saturday.