Also, DO NOT TRUST THIS FRAME EVER AGAIN. EVER. AGAIN. NEVER. EVER. DO NOT EVER USE THIS FRAME TO TRAVEL EVEN 10 FEET.
Having the downtube detached put extra stress on the top tube, so even though your "repair" has lasted 30mi, the cracking shows that the aluminum joint has bent. Bent aluminum is seriously weak. Toss the frame and be glad your stupidity hasn't killed you yet.