Is it permissible to say: "I was not, by Your supplication, my Lord, wretched" when supplicating for matters of this world or the hereafter?

There is no impediment for the supplicant to say in their supplication: "And I was not, by supplicating You, my Lord, unblest [or: unsuccessful]" for a religious or worldly matter, especially if the supplicant intends the meaning mentioned by the exegetes: that is, God has only ever been known to respond to prayers and not to reject what was asked.