a finishing repair is gonna look like a finishing repair unless you know exactly what you are doing and what colors to mix into the multiple coats of refinish to hide the repair. even for cheap-ass ikea, i'm sure they used a modern high durability finish and it probably won't be easy to match it.

lesson learned. biscuit joints aren't perfect. next time clamp something sturdy and flat across the finished side of the joint that wont stick to glue, like lumber, plywood, and wax paper.