The feast of Unleavened bread starts the day after the Passover, the supper was even the day before that, so at that time there would have been no need for the leaven to be destroyed. There was a full 2 days before the feast of Unleavened bread started.
Also consider the Greek language, artone is leavened bread and azumos is unleavened bread
Matthew 26:26-29, “And as they were eating, יהושע took bread, and having blessed, broke and gave it to the taught ones and said, “Take, eat, this is My body. And taking the cup, and giving thanks, He gave it to them, saying, “Drink from it, all of you. For this is My blood, that of the renewed covenant, which is shed for many for the forgiveness of sins. But I say to you, I shall certainly not drink of this fruit of the vine from now on till that day when I drink it anew with you in the reign of My Father.”
“bread” is word #G740 ἄρτος artos (ar'-tos) n., 1. bread (as raised)., 2. (also) a loaf of bread., 3. (specially, with G4286) the Proposal Show bread in the Holy Place of the tabernacle of Yahweh., 4. (during Passover) unleavened bread, matzah.
[from G142], KJV: (shew-)bread, loaf , Root(s): G142
Compare: G106, See also: G3957
“bread” is word #G142 αἴρω airo (ai'-rō) v., 1. to lift up., 2. (by implication) to take up or away., 3. (figuratively) to raise (the voice)., 4. (figuratively) to keep in suspense (the mind)., 5. (specially) to sail away (i.e. weigh anchor)., 6. (by Hebraism) to atone for sin.
[a primary root], KJV: away with, bear (up), carry, lift up, loose, make to doubt, put away, remove, take (away, up) , Compare: H5375
“bread” is word #G740, ἄρτος, artos, ar'-tos, From G142; bread (as raised) or a loaf:—(shew-) bread, loaf.
G740 ἄρτος artos ar'-tos Total KJV Occurrences: 61
• bread, 45 -
Matt 4:3; Matt 15:2; Matt 15:33; Matt 16:5; Matt 16:7; Matt 16:12; Matt 26:26; Mark 3:20; Mark 6:8; Mark 6:36; Mark 6:37; Mark 7:2; Mark 7:5; Mark 8:4; Mark 8:14; Mark 8:16; Mark 14:22; Luke 4:3; Luke 14:1; Luke 14:15; Luke 22:19; Luke 24:30; Luke 24:35; John 6:7; John 6:23; John 6:31; John 6:34; John 6:41; John 21:9; John 21:13; Acts 2:42; Acts 2:46; Acts 20:7; Acts 20:11; Acts 27:35; 1Cor 10:16; 1Cor 10:17(2); 1Cor 11:23; 1Cor 11:26; 1Cor 11:27; 1Cor 11:28; 2Cor 9:10; 2Thess 3:8; 2Thess 3:12
• loaf, 1- Mark 8:14
• loaves, 14 -
Matt 14:17; Matt 14:19(2); Matt 15:36; Mark 6:41(2); Mark 6:44; Mark 6:52; Mark 8:6; Luke 9:13; Luke 9:16; John 6:9; John 6:11; John 6:13
• shewbread, 1
Heb 9:2
1 Corinthians 5:7-8, "Therefore cleanse out the old leaven, so that you are a new lump, as you are unleavened. For also Messiah our Passover was offered for us. So then let us observe the festival, not with old leaven, nor with the leaven of evil and wickedness, but with the unleavened bread of sincerity and truth."
“unleavened” is word #G106 ἄζυμος azumos (a'-zï-mos) adj., 1. unleavened., 2. (figuratively) uncorrupted., 3. (specially in the neutral plural, by implication) the Passover week., [from G1 (as a negative particle) and G2219], KJV: unleavened (bread), Root(s): G1, G2219
From word #G2219 ζύμη zume (zï '-mee) n., 1. a fermenting agent (as if boiling up)., 2. (specially) leaven., 3. (figuratively, good or bad) a thorough, utterly complete change agent affecting itself and others., 4. (negatively) moral or mental corruption, depravity., 5. (positively) purity, integrity, a perfect condition., [probably from G2204], KJV: leaven , Root(s): G2204
“unleavened” is word #G106, ἄζυμος, azumos, ad'-zoo-mos, From G1 (as a negative particle) and G2219; unleavened, that is, (figuratively) uncorrupted; (in the neuter plural) specifically (by implication) the Passover week:—unleavened (bread).