"lost foothold" is a correct and usable phrase in written English.
You can use it when you want to describe something losing its stability or influence in a situation. For example, "Due to the changing political landscape, the company lost its foothold in the industry."
Charrington, a philanthropist and moral crusader, filed a police complaint against the Fulham chairman for "grossly unnecessary violence" but, as noted in When the Whistle Blows by John Kemp and Andrew Riddoch, his grievance was not upheld once it was established that during the scuffle "his tall silk hat remained on his head, he did not lose possession of his cigar, and never lost foothold".
They lost foothold in life as well as their sense of security and they became vulnerable.
Many homeless people lost footholds in subterranean passages beneath the World Trade Center.
Despite miles of skyscrapers and pavement in New York City, nature has not lost its foothold, at least not yet.
But she was not self-pitying, even when the business became an industry and women lost their foothold.
By the time the different divisions had been corralled into cooperating, Sony had lost its foothold in two crucial product categories: televisions and portable music devices.
Collins had not played a minute in the previous two games and had, by all appearances, lost his foothold in Coach Isiah Thomas's guard rotation.
National Express has lost its foothold in the Midlands after failing to secure the redrawn east Midlands and West Midlands routes, which went to Stagecoach and Go-Ahead respectively.
They lost their foothold north of the Ruvuma River early in the 18th century as a result of an alliance between the coastal Arabs and the ruler of Muscat on the Arabian Peninsula.
The art lost another foothold in Italy at the beginning of the same century, when changing attitudes about the world and about the function of art eliminated the very bases upon which mosaic had been built.
France's Groupe Danone finally lost its foothold in China this fall after a two-year legal battle with local beverage maker Wahaha.
