CEO Paul Anderson said about 20 sheets of the insulation material were blown off the structure and into the nearby Rastus Burn last Wednesday.
Contractors decided conditions were ''too dangerous'' to retrieve the sheets immediately, but all the material was recovered the next day.
The ''reasonably minor'' incident did not create an environmental hazard and did not warrant being reported to the Department of Conservation (Doc).
''It's a pretty inert sort of substance, and it was easily retrievable when the conditions were safe.
''If we'd lost some, that would have been of some concern, and we certainly would have talked to our Doc monitor on it.''
Doc Queenstown partnerships manager Greg Lind said he contacted skifield manager Ross Lawrence immediately after learning of the incident from a member of the public.
He was told that windy conditions, along with ice and snow from a previous storm, had made retrieving the sheets immediately too dangerous.
With that in mind, ''the delay was acceptable to me''.
The contractors were tasked daily with cleaning up any loose building materials, Mr Lind said.
''Ross Lawrence is very aware of the risk posed to kea, particularly by polystyrene and insulation material.
''I have asked him to strengthen the vigilance by contractors to reduce the risks to kea particularly, but also to ensure the material does not become lost in the alpine environment.''
Construction of the $20 million, three-level base building began last October and is due for completion in June.
Mr Anderson said contractors were working seven days a week to make up for time lost to poor weather, with up to 100 people on site some days.
''We're still on track for the building to be ready to open on June 20.''
The ground floor and basement were mostly closed in, the roof was close to completion and work was beginning on the first floor's interior.
