LondonLives may prove fruitful for you... Richard shows up a few times. He's in Bridewell at the beginning of October 1697, "under security for Transportacon" with a note that he's to be sent back to Newgate.
The same site, in one of its background articles, states:
Transportation dates from the seventeenth century, but the number transported was relatively low, because the cost of the voyage had to be paid for either by the convict or a merchant or shipowner.
One possibility is that he could not raise the funds for his journey, nor find a merchant to buy his indentured labour (and pay for jail fees, paperwork etc.) He'd be most attractive as an investment if he had useful skills and/or was young and healthy.
It's also the case that after 1670, both Virginia and Maryland passed laws prohibiting transportation, which will have restricted the market for his services.
I do note that the Ordinary's Account of 3 November 1697 doesn't explicitly mention him being hanged, although the deaths of others are mentioned. Perhaps the Ordinary wasn't present at the death.