A gang of six masked men raided a recycling company in Slinfold, demanding cash and gold.
The intruders entered Duesmann and Hensel Recycling Ltd, Maydwell Avenue, and tied up the woman receptionist and a man working there, stealing their car keys and wallets.
A statement from Sussex Police said: “They also demanded cash and gold, which are not held on the premises.
“However they then fled when they became aware that another member of staff elsewhere on the premises had realised what was happening and was raising the alarm via an adjacent company.
“The two victims were shaken but not physically injured.”
The suspects are believed to have arrived in two white vans, one of which was abandoned at the scene.
Police are still looking for the second, described as a white Transit van.
DS Sian Harding said: “We would like to hear from anyone who was in the area late on Friday afternoon and who saw this white van or any other suspicious activity. Please contact us via 101 quoting serial 1418 of 18/1. You can also call independent charity Crimestoppers anonymously on 0800 555 111”.