The phrase "lost footing" refers to a loss of balance or stability, either in a literal or figurative sense. Synonyms for this phrase include "slipped," "stumbled," "fell," "tottered," "tumbled," "wavered," "faltered," "foundered," "struggled," and "tripped." Depending on the context in which the phrase is used, different synonyms may be more appropriate. For example, "stumbled" could be used to describe a physical misstep, while "foundered" might be used in a more metaphoric sense to indicate a failure or downfall. Whatever the situation, these synonyms all convey a sense of loss or lack of stability.