# In Sidekiq, when you use perform_async() method, the job is immediately enqueued and could possibly be found in Sidekiq::Queue if the worker has not picked it up yet:
queue = Sidekiq::Queue.new("mailer")
job = queue.find_job(jid)
# And when you use perform_in(1.hour, ...), the job is scheduled to run sometime later and can be found in Sidekiq::ScheduledSet, in this case, for 1 hour:
ss = Sidekiq::ScheduledSet.new
job = ss.find_job(jid)
# So, in this case, after 1 hour the job will possibly be enqueued which means the job will then be found in Sidekiq::Queue like before.