Long story...I had my barn's farrier trim my horses feet on his last visit because my farrier had moved away. My horse got trimmed too short and he took to standing in a mud puddle in his stall.
I was hard-pressed to believe the thrush caused laminitis so I asked the question of "Google" and didn't find anything that says thrush can cause laminitis.
It's those words "trimmed too short" that, in all likelihood, caused the laminitis. The other farrier most likely cut into the live sole and VOILLA! there's the laminitis.
The thrush did occur from the horse standing for long periods in the mud, in an attempt to cool his hooves from the fever inside the hoof.
Standing in mud to cool their hooves is a natural thing for them to do. It's why folks always suggest leaving a mud puddle in front of water tanks.
The severe thrush happened from lack of attention to the hooves which, is tough to do when a horse is in a boarding situation and the Owner can't get there every couple days. 95% of BO's and their help are not going to clean and medicate the hooves on someone else's horse.
It isn't this BO's fault your horse got trimmed too short but they have a responsibility to keep waterers, etc free of leaks not only for the health of the horses but their water and/or electric bill.
If you happen to be in a drought area, I'd be honked off if I was the neighbor trying to conserve my water while your BO was allowing precious water to leak onto the ground.
Point-being, if there were already existing factors that make you un-happy at this barn and the laminitis & thrush are the icing on that moldy cake, move your horse as long as the horse is going to a better place and you can afford to write the check
The thrush won't go away just moving him; if it's that bad, I am sorry but somebody is going to have to tend to his hooves 2 - 4 times a week and that doesn't just mean picking and pouring Koppertox in. I think Koppertox is useless in bad thrush situations but I'm not a vet.
The hoof needs soaked and scrubbed with a hard bristled brush (not a wire brush as the frogs are very sore and that will really sour a horse on hoof work.
You could soak each hoof for 10 - 20 minutes in a mix of a gallon of water, enough betadyne or Triodyne to turn the water dark brown and no more than a CAPFUL clorox. Then scrub with the brush again, pat dry, pour the Thrush meds on the affected areas.
If you don't have betadyne, Dawn dish soap is cheaper and is an anti-bacterial/fungal soap. Follow the same process.
Regarding farriers, when looking for the next one, I would be adamant in letting them know what has happened and you don't want the toes pulled back so tight the next time. Even if that means getting him re-set one or two weeks earlier.
You really shouldn't be riding him until his hooves recover from the laminitis and the thrush is down to barely noticeable. I would consider leaving him barefoot for awhile; it would save you some money. He doesn't need shoes for laminitis. One of my foundered on grass in March and rotated 8 - 9 degrees on the LF and 5 degrees on the RF. He's been out in pasture every day since in Boots with 3/8" partial foam pads.
His founder was severely aggravated by the barefoot trimmer that trimmed him too short and cut into his live sole. He also cut too much heel which resulted in severely strained flexor tendons. My horse was pretty much crippled to where nobody knew if he'd pull thru and walk normal again.
Shoes were never suggested by my vet or the equine podiatrist who now trims him. Just let him roam around with boots and pads until further notice. He's made jaw-dropping progress in three short months.
Hope this helps