This verse is speaking of whomever one follows in a general sense, whether or not that person is physically near them or they even meet them. So a person's Imam could be the Prophet (S), Imam Mahdi (A), a scholar, or a spiritual leader; or it could be someone else entirely, like a philosopher, author, or political leader. Whoever guides your way of thinking, way of life, and identity, and whomever you obey and associate yourself with and prioritize is your Imam.