Dearest dave
You have raised a good point, but do not worry, fetch the Priest. You are right Jesus should never be left alone when the Eucharist is exposed in the Exposition and Adoration of the Blessed Sacrament, this is not only because it is irreverent to do so, but because of protecting the Eucharist from desecration, who knows who will wander into the church.
Please don’t spend your last minutes with your Jesus worrying, tell Him you are about to leave and do not want to leave Him alone, then spend your time loving and adoring Him.
If there are no lay people about, go and get your Priest and let him know no-one is in the church and you are about to leave, if you do not have to leave stay and love your Jesus and protect Him also.
God Bless you Dave and much love and peace to you
Teresa