If you are close to the scheduled time to switch to your next aligner, you may be advised to move forward to the next set. However, if the aligner is lost early in the wear period, do not proceed to the next stage without professional guidance.
Instead, contact your certified provider as soon as possible. They will advise you based on your individualized treatment plan and arrange for a replacement if necessary.
In the meantime, if available, wear your previous aligner to minimize unwanted tooth movement until further instructions are provided.