Some more search ideas that you may not have thought of:
Take the bed totally apart. Your hand may have dangled over the side and the ring could have either fallen between the sheets and lodged between the box spring and mattress. Lift the box spring out of the frame and look there too. The ring could have lodged between the frame and box spring.
If you have animals (especially cats), check the place where they take their toys and treasures. One of them could have found the sparkly object and taken it to their favorite spot. Check the wall edges under and near the bed. If they're like my cats were, they probably played soccer with the shiny object and it got wedged between the baseboards and carpet under the bed. Dim the lights and use a flashlight around the edges of the room. The ring will reflect in the light and make it easier to spot.
If you did any cooking or baking that day, check the bins that hold any of the ingredients you may have used and had your hands into: flour, sugar, etc.
You say only one drain is big enough for the ring to fit in. Check the other drains anyway. Rings (like coins) are amazingly agile and can get into the oddest places that they shouldn't fit into.
Check the towels and robes you used to dry off and keep warm in before dressing. The clamps that hold the stone in the ring could have snagged on the terry cloth or knitted fabric and it is still stuck to the item.
When you were gardening, did you have your bare hands in mud and water at any time? If so, check those places in the garden. Mud and water make a great lubricant for a ring. How about sacks of gardening soil or fertilizer? Did you have your bare hand in those at any time? If so, check those.
You said you picked up some deck furniture. Did you have to do any assembly of it? Check the nooks and crannies of the deck furniture. If you still have the boxes, check the packing materials.