Complex sentence: Because Coffin demanded to see search warrants and slave-ownership papers before allowing entry to his home, it was never searched and escaping slaves had been transported to other locations by the time the slave hunters returned with the documents.
Split into simpler sentences: Because Coffin demanded to see search warrants and slave-ownership papers before allowing entry to his home, it was never searched. Escaping slaves were transported to other locations by the time the slave hunters returned with the documents.