In your study, No One Knows The Day or Hour you said, “In Rev. 16:15 the world is well into the Great Tribulation, so the Lord’s warning is for Tribulation believers who will be responsible for keeping themselves saved during the most terrifying and dangerous time the world has ever known.” This means there will be people that will get save during the Trib; after the church is gone from the earth. If that’s the case there has to be another resurrection for the dead because believers will die during the trib. Is there a scripture saying that there is a third Resurrection?
Instead of thinking of the number of resurrection events, we should think of the different types of resurrections instead. There are only 2 types of resurrections, one for believers and one for unbelievers.
In 1 Cor. 15:20 Paul wrote that the Lord Jesus was the first fruits of the first resurrection. 1 Thes. 4:16-17 and 1 Cor. 15:51-53 say there will be a resurrection along with the rapture of the Church. Daniel 12:1-3 says all Jewish believers from the Old Testament will also be resurrected at the end of the Great Tribulation.
Rev 20:6 says the tribulation saints will be resurrected at the time of the 2nd coming and are part of the first resurrection. That means everyone resurrected from the Lord’s time until the 2nd Coming will be part of the first resurrection. This is a resurrection to eternal life.
The resurrection of the unsaved will take place at the end of the Millennium (Rev. 20:11-15). This is the second resurrection, a resurrection to eternal suffering.