I borrowed ROSG 400 shares in the morning at 8 am and set limit sell price at $10. At around 10 am, I modify the order to market order. But it seems the original order is cancelled and the new market order does not go through. The borrows is gone. I chat with the customer service and they said it is possible that the borrow is allocated to someone else. It is strange since I am using market order. If there is no shares, thinkorswim will reject the order. So I assume no one should try to borrow during the time of computer modification the order. Unless they have a waiting list? I do not know what's happening in Thinkorswim. Anyone has such experience and know the exact reason? Because I think it is OK to set a higher sell price first and later set a lower price to execute.
It sounds like they gave you a locate for an order not for the day, which is more typical. When you changed the order, you lost the locate. This is not typically the way locates are done at other firms.
your response has both a correct and possibly incorrect component. at IB the locate is for a given moment of time when you enter the order. if your order is not executed immediately you are part of cue based upon time and price. this is an excellent policy as it doesn't allow some idiot from tying up shares when he has an ulterior purpose not to get the order executed. also at IB if you change your order to market you don't lose your locate.
Except he is not at IB. He stated ThinkorSwim which is TD. Also, FYI, your not asking for a borrow. Your asking for a locate. The difference is that you're asking permission to short a stock that is NOT on the easy to borrow list. That way you can enter the order. You can buy it back later and not have to borrow the security. Very few firms offer a pre-borrow which allows them to make delivery on time. Just because you get a locate, it does not mean the firm won't fail on delivery and you can be bought in.
perhaps you should read your own response. you brought up the subject of other firms. "This is not typically the way locates are done at other firms. " I gave IB as an example, as the way they handle the situation in most cases.