If there is no divorce record of your ancestor and you think they got divorced, consider that they may have never legally gotten divorced.
If that’s the case, make certain you have exhausted all records on the “divorcing” ancestor. If they owned real estate, check all the land records as the spouse may have had to waive various rights to the property before it could be sold if they were still married. A purchaser is going to want to have clear title. If they were divorced or single at the time of the sale, the deed may reference their marital status at the time of the transaction.
Check for probate records on both members of the “divorcing” couple. If the couple were still legally married, a surviving spouse would have an interest in the estate.
If applicable, check for a military pension and widow’s pension. If the female partner of a separated couple survived her husband, she may have still applied for a pension.
Make certain you have looked in all appropriate courts for the record of the divorce. In the United States divorces are typically granted by a local court where the husband or wife lives or has established sufficient length of residence. That may not be where you think. Try searching online newspapers in case a reference to the court case made the local newspapers.
Try a Genealogy Search on GenealogyBank.