Probably not. If the lender can show that the mortgage has been properly assigned to the current holder, the court will usually allow the foreclosure without the original promissory note. For a more definitive answer, you should consult with an attorney in your area who does foreclosure defense.
Disclaimer: This answer is provided for informational purposes only, does not constitute legal advice, and does not create an attorney-client relationship. Actual legal advice can only be provided after completing a comprehensive consultation in which all of the relevant facts are discussed and reviewed.
There is no simple answer to this question. The law in Florida says that a plaintiff does not necessarily have to produce the original note in court, if it can properly prove grounds to reestablish a lost note. So, that is what they try to do if they really cannot come up with the note.
Defending a case on this basis is a complex undertaking, and entails sailing into a heavy headwind. Be sure that the mortgage company will push back very hard. We have cases we are defending where the mortgage company now has three different law firms working on their side to oppose us. In addition, many judges really don't understand the legal issues clearly, and give the benefit of the doubt to the mortgage companies.
The odds of a result where the borrower "gets the house free and clear", even after being lent mortgage proceeds, are very long. If anyone is encouraging you to think such an outcome is reasonably do-able, RUN the other way. Even if a defense is successful, which is in itself a tall order, succeeding would mean that the foreclosure cannot proceed. While that may end that round, it still does not result in a free and clear house.
Attacking a foreclosure plaintiff's right to foreclose is often a sound and worthwhile strategy, and one that we frequently utilize. However, it is important for borrower to understand that exactly how it will go depends on many things. Most borrowers are not looking for a free and clear house - what they want is a reasonable opportunity to force the mortgage claimants to a fair outcome, and consider that to be a huge win (which it is).