Some of the hard evidence from Christian iconography in the burial catacombs is an eye opener.
Thanks for the link. I was scrolling through and noticed this section which sounds like it could be what you are referring to. I thought it was even interesting enough to warrant being placed on your thread so hope that's okay...
Testimony of the Catacombs.
An illuminating side-light is cast on the opinions of the early Christians by the inscriptions and emblems on the monuments in the Roman Catacombs.12 It is well known that from the end of the First to the end of the Fourth Century the early Christians buried their dead, probably with the knowledge and consent of the pagan authorities, in subterranean galleries excavated in the soft rock (
tufa) that underlies Rome. These ancient cemeteries were first uncovered A.D. 1578. Already sixty excavations have been made extending five hundred and eighty-seven miles. More than six, some estimates say eight, million bodies are known to have been buried between A.D. 72 and A.D. 410. Eleven thousand epitaphs and inscriptions have been found; few dates are between A.D. 72 and 100; the most are from A.D. 150 to A.D. 410. The galleries are from three to five feet wide and eight feet high, and the niches for bodies are five tiers deep, one above another, each silent tenant in a separate cell. At the entrance of each cell is a tile or slab of marble, once securely cemented and inscribed with name, epitaph, or emblem. 13 Haweis beautifully says in his "Conquering Cross:" "The public life of the early Christian was persecution above ground; his private life was prayer underground." The emblems and inscriptions are most suggestive. The principal device, scratched on slabs, carved on utensils and rings, and seen almost everywhere, is the Good Shepherd, surrounded by his flock and carrying a lamb. But most striking of all, he is found with a goat on his shoulder; which teaches us that even the wicked were at the early date regarded as the objects of the Savior's solicitude, after departing from this life.13
Matthew Arnold has preserved this truth in his immortal verse:14
"He saves the sheep, the goats he doth not save!"
So rang Tertullian's sentence on the side
of that unpitying Phrygian sect which cried,--
"Him can no fount of fresh forgiveness lave,
Whose sins once washed by the baptismal wave!"
So spake the fierce Tertullian. But she sighed,
The infant Church,--of love she felt the tide
Stream on her from her Lord's yet recent grave,
And then she smiled, and in the Catacombs,
With eyes suffused but heart inspired true,
On those walls subterranean, where she hid
Her head in ignominy, death and tombs,
She her Good Shepherd's hasty image drew
And on his shoulders not a lamb, a kid!
This picture is a "distinct protest" against the un-Christian sentiment then already creeping into the church from Paganism.