Hi Joseph,
As you noted, the cotyledon and leaf shape are wrong for Salvia splendens. 'Yvonne's' seedlings should look like other Salvia splendens seedlings that you've grown.
Also, note the palmate leaf venation. Salvias have pinnately reticulate venation (main veins are pinnate, then branch into smaller reticulate veins.)
Your seedling looks a lot like a Malva family seedling of some sort. What did the seeds look like?
