A Question of Private Consecration

Fr. Anselm comes to say Mass at St. Egregia for one Sunday while your pastor, Fr. Bertrand, is on vacation. Fr. Bertrand had also asked Fr. Anselm to make a few sick calls in the parish after the mass. Seeing that the sanctuary lamp next to the tabernacle is lit, Fr. Anselm does not save any of the consecrated bread from the Mass. When Mass is over and Fr. Anselm goes to the tabernacle to fill his pyx with the reserve sacrament, he is astonished to find it empty! Frustrated, Fr. Anselm finds some unconsecrated hosts and privately says the eucharistic prayer to consecrate them for his communion calls. Were these hosts validly consecrated?

Analyze this case:

Variation:

Fr. Anselm comes to the tabernacle and finds a zip-lock bag of hosts there. Thinking them to be consecrated, he takes a few to make his sick calls. Monday morning he discovers that the hosts he took were not consecrated after all. Were the communions he administered valid?